In order to explore the variation rule and correlation between forest canopy structure and understory light, four fixed monitoring sample plots with area of 1 hm² (100 m×100 m) were selected in Baiyun Mountain National Forest Park, Henan province, including Artificial forest, Twice-cut forest, Once-cut forest and Undisturbed forest in this study. The data of canopy structure and understory illumination were obtained by hemispherical imaging. Results show that 1) with the intensity of man-made interference decrease, the canopy coverage and leaf area index increased, while the scattered radiation and direct radiation decreased. 2) The canopy coverage and leaf area index of Twice-cut forest were the largest, but mean leaf angle and light transmittance were the smallest. The understory light (direct radiation and scattered radiation) were significantly negatively correlated with canopy coverage and leaf area index, while the understory scattered radiation had the strongest negative correlation with canopy coverage and leaf area index. 3) Because of the difference of canopy structure, the communities in different man-made interference stages formed specific illumination environment in different communities. The results of this study enrich the research data of forest canopy structure and understory illumination dynamics in the transition zone of warm temperate-subtropical transition region, and provide scientific basis for forest restoration and reconstruction in this region.