Abstract: During the processing of femtosecond laser ablation of monocrystalline silicon, the effective gray area in the spot image collected by the charge coupled-device (CCD) camera was difficult to distinguish with the background. In order to solve this problem, a method combining the principal component analysis with the adaptive histogram equalization of limited contrast was proposed to enhance the spot image, and then a detrending cross-correlation analysis method was proposed, which analyzed the long-range correlation of gray features and geometric features for the spot sequence images. The results show that the gray features of the spot sequence images have a strong long-range correlation with the spot texture contrast and the spot area, and they show a strong inverse correlation with the texture homogeneity. The correlation relationships are used to predict the gray features in the subsequent micro-groove processing.