Reliable operation of the power transformer is the basis for the security and stability of power system operation. The traditional state evaluation methods for transformer are inadequate, especially in device properties and environmental information. This paper proposed a transformers environmental and properties state evaluation method based on the defects analysis. Firstly, statistics transformer defect cases in Guangdong. According to the causes, classify the defects as leakage (from tank, oil conservator, and other main parts of transformer), moisture, and component fault, overheat, rust, filthy, exceed the standard. By the statistics, it shows that moisture, leaks, component failure, overheating defects are the main causes. Secondly, analyze the relevant between main causes and influence factors such as operational life, voltage levels, temperature, and rainfall. Then score each factor, according to the environment of the transformer, to evaluate the specific defect's risk. The code of points comes from count general distribution of defect. According to the distribution law of the factors, the basic risk criteria are determined by the total defect's distribution, and the different kinds of influence risk criteria are determined by the distribution characteristics of specific defects. At last, summarize specific defects score to get the corresponding operation and maintenance strategy, which are divided into 4 grades, healthy, potential, preliminary, and Critical. In the end of paper, test the assessment method with a running transformer case. The test result shows that the assessment method successfully evaluates a power transformer's device properties and environmental state.