According to the black spot detection principle and black spot halo characteristics of the microchannel plate, a detection method was designed. The circle extraction technology was used to realize the radius and circle center extraction of the fluorescent screen image, and the gaussian Laplacian was used to realize the coarse detection of the target black spot. Based on the characteristics of black spot presenting halo in the periphery at different voltages, the black spot halo was extracted by using the histogram equalization with restricted contrast and combined with the threshold segmentation of the halo detection method. The test results show that the proposed method can effectively distinguish the fluorescent screen scratches, dust and black spots of microchannel plate, so as to realize the automatic extraction of black spots.