Abstract: We use the fruit flies optimization algorithm to optimize smoothing factor of generalized regression neural network, and thus proposed the bullet scratch depth modeling method based on the optimization of the generalized regression neural network with improved fruit flies optimization algorithm, and the method is much better than the unoptimized generalized regression neural for function approximation.In the end, take the generalized regression neural network without optimization method, the unoptimized generalized regression neural network with original fruit flies optimization algorithm and the BP neural network into comparison, the performance of this method is superior to the other three methods, it verified the effectiveness of this method in the bullet scratch depth prediction.