Precise location of laser spot in laser precision measurement is always an important research direction. Laser has the characteristics of good direction and small divergence, so it is widely used in aerospace, weapon systems and optical measuring and testing instruments. The accuracy of the laser spot center location can directly determine the precision of measurement. Aiming at positioning the center of laser spot, in the foundation of researching the limitation of the practical application of the common laser spot center location algorithm, this paper proposes a method of laser spot center localization based on sub-pixel interpolation, which can effectively improve the signal noise ratio (SNR) of laser spot image, reduce the influence of the background noise and thermal noise. The algorithm firstly uses the threshold value decision to exclude the interference of the light of the image, and then use the improved sub-pixel interpolation algorithm for image edge detection to obtain the edge image, and finally using the circle fitting method to obtain the positioning center. Through the experiment of processing of laser spot image, the results show that improved algorithm proposed in this paper has higher positioning accuracy than the traditional centroid, and satisfies the need of laser precision measurement in reliability, positioning accuracy and noise resistance and other aspects, at the same time, the computational complexity of this algorithm is low, can greatly save the system resources, and it can be used for the processing of the video images in the hardware and software.