Due to the differences of various infrared cameras parameters and the surroundings influence,the robustness of the threshold auto-selection algorithm in infrared images segmentation has not been well resolved.Based on the mechanism of infrared imaging,we presented a new solving scheme and put it into practice.Firstly,the image histogram was clustered by K-means clustering method,and then the distribution characteristic of the cluster centers was analyzed in detail and the threshold for image segmentation was determined.This algorithm doesn’t need to equalize the image before segmentation and assume the distribution of the background.Experimental result shows good robustness.