Infrared warship target detection is one of the most important techniques in ship automatic recognition and tracking. Because adaptive capacity of the existing method is poor when warship target imaging gray appears bipolar (the intensity of warship is higher or lower than background),a new infrared warship target detection method is proposed. In order to suppress background interference,an image is processed by using mean shift filter. Compared to the traditional method,the ROI is obtained by vertical gradient projection. Finally,automatic ship target detection is realized by suppressing false corners and extracting warship corners. Experiment results show that the proposed algorithm can get good performance in bipolar target detection especially when the warship has different gray scale values.