Radar detection of in-shore targets has been a difficult problem in target recognition for a long time. It is difficult to detect and identify in-shore low-speed ship targets. However, ship targets have better infrared radiation characteristics which can be fully utilized in the detection process. According to these characteristics, an image processing method based on Top-hat transformation and OTSU is proposed. After open-operation reconstruction, the Top-hat transformation is used to enhance the contrast between the target and the background in an infrared image. To detect targets, the threshold values of the image are segmented by OTSU according to the gray-scale characteristics of the image. The experimental results show that the algorithm can effectively detect in-shore ship targets and is of a certain practical significance to the recognition of in-shore targets.