Infrared spot center location is the key technology of infrared optical measurement. Aiming at the problems of low infrared spot resolution, poor contrast, blurred target edge and low accuracy of spot location, an infrared spot location algorithm with high precision and small size is proposed in this paper. For infrared image pre-processing, the image is pre-processed by single filter and combined filter, after which the sub-pixel level coordinates where the spot center is located are determined by the IR spot center-of-mass and form-center methods. The results show that the error of this algorithm is less than 0.035 pixels compared with other algorithms in the infrared spot image with noise pollution, which ensures the high-precision positioning of the infrared light plate.