The method of Mean Time Between Failures (MTBF) is used commonly to evaluate the status of CINRAD/SA radar operation, which ignores the fact that different parts have different influences on the operation status of radar. However, only numerical degrees cannot reflect the quality of maintenance work. A new method is proposed, in which CINRAD/SA radar is divided into parts according to the radar structure, and after each part is given a weight on the basis of its influence on the operation of radar, the ranking of radar operation and its grade of membership are computed by means of membership function. Simulation using the operation logs of 8 CINRAD/SA radar shows that the algorithm is more accurate and effective than MTBF approach.