Grounding technology plays an important role in ensuring safe and reliable operation of the power system and the personal safety. Grounding resistance as an important ground parameter, dictate the degree of electrical safety. This paper introduces the basic principles of testing the grounding resistance, the testing methods and the necessity. According to the actual application and comprised data. This paper introduces the advantages of the multi-needle grounding pole, and it can be applied to the rock, the frozen ground and the other hard permafrost soil. Using it, we can make the ground resistance testing would not be affected by the seasonal environment influence, and it can be applied to the grounding resistance test in the electric power and mining enterprises. Introduction In recent years, many substations in Fushun have expanding accidents caused by the lightning .Most of the accidents is associated with the unqualified grounding resistance. Grounding net plays an important role on working grounding and protective grounding. When the grounding resistance is too large, it will cause an accident. It will increase the neutral point voltage offset, and it may cause sound phase and the neutral point voltage over high, and it will exceed the level of the insulation requirements and cause equipment damage[1-3]. When lightning or thunder waves attacks, Current increases, which will produced a high residual voltage. The equipment nearby will be threatened by the counterattack voltage. Apart from this, the quality of grounding resistance is directly related to the safety of operation and maintenance staff. Therefore, we must strengthen the regular monitoring of grounding resistance, thereby ensuring safe and reliable operation of the power grid[4, 5]. The basic principle of grounding resistance test Grounding resistance refers to it when the current through the grounding body flow into the soil, that will form the resistance by the soil around the grounding body. Grounding resistance add the resistance of attachment between grounding body, grounding body itself , the resistance between grounding body and soil .The numerical value is the ratio of grounding body voltage to the earth and the current through the grounding body. If the resistance is calculated with operation frequency alternating currents, we call it operation frequency grounding resistance. If the resistance is calculated with the surge currents through the grounding body flow into the earth, we call it surge grounding resistance. The basic method of grounding resistance test (1)Current voltmeter method Current voltmeter method applies to measure large power station or transformer substation grounding grid grounding resistance. By the current voltmeter method, the test wiring of measure grounding resistance is shown in figure 1. 4th International Conference on Machinery, Materials and Computing Technology (ICMMCT 2016) © 2016. The authors Published by Atlantis Press 1387 Fig. 1 the test wiring by the current voltmeter method 1—isolation transformer 2—autoformer regulator 3—grounding grid 4—Auxiliary voltage pole 5—Auxiliary current pole 6—earth surface Usually, according to the pole arrangement when we test the grounding resistance, we take the 0.618 and 30°testing method. Voltage current line arrangement (0.618 testing method), Generally we select current line D for the largest diagonal in grounding grid length of 4 ~ 5 times, voltage line D is about 0.618 * D. Voltage current triangle arrangement(30°testing method), To compare with line arrangement, Voltage current triangle arrangement has the advantages of little influence on mutual inductance between down-lead. At this point, we general take d=D≥2 times the length of the diagonal,θ≈30°. (2)Grounding resistance meter method Grounding resistance meter method generally apply to transmission line tower, independent lightning rod, microwave tower and other small grounding device ,grounding resistance measurement. Normally we adopt ZC-8 grounding resistance meter to measure grounding resistance, the connection is shown in figure 2. Fig.2 ZC-8 grounding resistance meter measuring grounding resistance The necessity of grounding resistance testing Check whether the new input grounding grid accord with the design rules. During operation ground lead and null line sometimes were affected by the damage of external force or chemical corrosion, etc. Damage or fracture phenomenon is always happen. The soil surrounding the grounding body will also be changed, because the drought and freezing affect the grounding resistance. In order to ensure the reliability of ground connection and connect to neutral, we must make regular inspection and test on the grounding device. Problems on site testing At present, we use one or more steel tube whose diameter is 25-50mm, length is 500mm for voltage (current) grounding in 10kV system grounding resistance testing. We insert it vertically into the ground about 400 mm. Fushun is located in the mountains, the soil is very hard, especially in the winter the soil will form the permafrost. Grounding pole is hard to insert into soil, after inserting reluctantly, grounding pole cannot contact with the soil tightly, so that we cannot get the real data of grounding resistance. It directly affects the engineering construction progress, delivery of current and recovery operation, etc.