Abstract: In order to enhance the weak and asymmetrical image of small laser spot and suppress the noise information, eliminate unstable laser spot effect on the calculation results, a new method was proposed in this paper. Firstly, a multi-dimensional image cube was constructed by many images captured in different time, the primary information was concentrated in the first dimensional image, the correlation of each dimensional image was removed. Secondly, the first dimensional image was divided into laser spot and background by Kmeans method, the classified image was processed by mathematical morphology, the edge of largest spot was searched as edge of small laser spot. Finally, the least square method of circle fitting was used to calculate small laser spot center. The experimental results show that the method can improve the accurate rate on checking the weak and asymmetrical laser spot, the binary laser spot area obtained by new method is 97.15% of ideal spot area, the error of small laser spot center and radius is less than 2 pixels, and realize the accuracy measure of small laser spot in the integrated diagnostic system.