Aperture expanding and frequency upgrading of full steerable antennas make the electrical performance of the antennas difficult to guarantee, and that radio telescopes operate in a complex environment, so it has to improve the performance by some methods like mechanical or electronic compensation. To control the pointing accuracy and the detecting distance of antennas, we must adjust the position and the surface shape of shaped reflectors, in another word, the active surface adjustment is the most effective way. Therefore, this article describes the situation and status of applications of active surface adjustment. Then, it summarizes the basic principle and the applications of active surface adjustment and particularly analyzes the key technologies which include the calculation of actuator movement, the block design of main surface, the actuator design, the active surface control system and the surface profile measuring. The comparisons among four large radio telescopes of the world are discussed, which have used active surface technology. At last, it points out some suggestions on the future research of active surface technology of large radio telescopes such as QTT.