Infrared image registration technique is the core of circuit board fault detection system.In order to improve the accuracy and efficiency of circuit board infrared image registration，an image registration algorithm based on ROI gray compression is proposed.First，Otsu method is used to extract circuit board infrared image ROI.Then，the ROI gray value is made linear compression.Finally the best image transform parameters are searched like x translation，y translation，rotation，scaling by mutual information calculation.The simulation results show that the image compression algorithm base on ROI can significantly reduce the registration time.The environment temperature difference of two images is larger，the registration accuracy is better.