With the application of the software system in large phased array radar (LPAR), the safety problem caused by the software system has been widely concerned. Aimed at the safety problem of LPAR software system, firstly, the software failure mode and effects analysis method is used to analyze the safety, and the weak links of the systems are found. Then the targeted safety design is carried out and effective improvement measures are put forward. Finally, the improved fuzzy analytic hierarchy process is used to evaluate safety. It is proved that this method can effectively analyze the safety problems of the LPAR software system, find out the failure reasons affecting safety, improve the design of weak links of safety, and evaluate the safety of the whole LPAR software system.