According to the characteristics of infrared projectile target images,and on the foundation of analyzing several histogram-based threshold segmentation algorithms,a method for improving the real-time performance of such algorithms was studied.Considering the feature of fixed pixels of projectile images,we proposed a rapid algorithm based on p-tile histogram.On the segmentation effectiveness,the algorithm can improve the accuracy for extracting the projectile target.Compared with the traditional histogram-based thresholding algorithms,the algorithm can decrease the running time by 30%.Simulation based on Matlab shows the effectiveness and real-time performance of the algorithm.