Aimed the problem of test equipment electro hydraulic control and its working stability, a control system of test equipment is designed based on programmable logic controller (PLC). The principle figures of hydraulic system and three kinds of control circuit were given. The I/O interface figure of PLC servo control was determined, and the PLC control program was compiled. Then, on the basis of four different working conditions of test equipment, analysis methods of its stability were discussed, and a stability monitoring software was designed and visual simulated. The results show that the stability is better when test equipment is under the fourth working condition.