This paper proposes a false alarm reduction method on radar equipment BIT based on BP neural networks optimized by Genetic algorithm in order to eliminate BIT false alarm which is reduced ineffectively by existing fault diagnosis methods. Firstly this paper introduces the principle and corresponding learning algorithm of BP neural networks optimized by Genetic algorithm. Then in view of the characteristics of radar BIT, this paper constructs a fault diagnosis system based on GA-BP neural networks by using Matlab to simulate the process of fault diagnosis with nine respective fault characteristics and eight typical fault examples of Radar transmitter. The diagnosis result indicates that the GA-BP neural networks can identify and locate the fault of sample effectively, and the false alarm of BIT can be reduced, which improves the fault diagnosis ability of radar system.