Infrared overlapped fingerprint image is a kind of complex infrared image in the field of criminal investigation. The information of the image is uncertain，and the fingerprints are overlapped. How to accurately extract the overlapped target is a difficult problem in the field of criminal investigation. To solve this problem, an infrared criminal investigation overlapped fingerprint target extraction algorithm based on the fusion of variable threshold value and coordinate transformation is proposed in this paper. Firstly, the threshold algorithm is used to extract the whole and the overlapped fingerprint image. Then the coordinate transformation method is used to filter the independent regions of the two parts of the images. Finally, the contour fusion algorithm is used to fuse the two parts of the image, so as to obtain the extraction result of the whole fingerprint target. In order to make the extraction results more visual, the coordinate transformation method after the image rotation operation to extract a single fingerprint target is adopted in this paper. Experimental results show that, compared with other target extraction methods, this method has higher accuracy and integrity in the whole and single fingerprint target extraction.