Laser plasma spot center extraction due to the poor effect of image noise reduction, the center extraction under complex background is inaccurate, so a new subpixel extraction method of laser plasma spot center under complex background is designed. In this method, the multi-graph average method and Gaussian filter algorithm are combined to process the laser plasma spot image with noise reduction and complete image pre-processing. Zernike moment method is introduced to extract the laser plasma spot center, and the circle fitting method is adopted to optimize the algorithm to achieve the subpixel extraction of the spot image center. The experimental results show that when the proposed method is used to extract the laser plasma spot center subpixel under complex background, the image of the spot center extracted by the proposed method is more clear, and the signal-to-noise ratio reaches more than 47.0dB, and the absolute error of the extracted center position is only 1mm, this method has high extraction accuracy and better image quality.