Abstract: The cumulic epipedon of Lou soil is formed by dung stacking till slaking. The thickness of cumulic epipedon can reflect the fertility level of Lou soil and the effect of human activities on the soil forming process. The investigation on the thickness of cumulic epipedon and the analysis of its natural and human factors can provide scientific basis for the nutrient-holding capacity and the classification of Lou soil. In this study, grid sampling sites (5 km × 5 km) were designed in the Guanzhong region to investigate the thickness and spatial distribution characteristics of cumulic epipedon using 273 profiles of Lou soil. At the same time, 13 influencing factors were selected to analyze the correlation between the cumulic epipedon thickness and the natural and human factors, with a quantitative analysis of their importance by random forest regression. The thickness of the cumulic epipedon in Guanzhong region ranged from 14 to 130 cm, with an average thickness of 55 cm. Its coefficient of variation was 34.28%, belonging to the medium degree of variation. It was relatively high distributed in Hancheng, Heyang and Chengcheng (60-80 cm dominant) areas in the east and Chencang, Qishan and Wugong (60-70 cm dominant) areas in the west. The thickness of cumulic epipedon had a significant positive correlation with latitude and longitude, and a significant negative correlation with slope, temperature and humidity. The influence of human factors was directly proportional to the increase of population and inversely proportional to the decrease of per capita cultivated land area. The maximum thickness of cumulic epipedon mostly appeared in the range of 9-13 km from the river. The comprehensive interpretation of the 13 influencing factors was 64.36% for the thickness of cumulic epipedon. The results of importance ranking showed that the change of per capita cultivated land area had the most significant effect on the thickness of the cumulic epipedon, followed by the change of population. The thickness of cumulic epipedon in the Guanzhong region was higher in the east and west, and slightly lower in the middle, and the high points were distributed sporadically. The formation and distribution of the cumulic epipedon were more deeply affected by human factors than the "five soil forming factors", especially gradually increased with the development of productivity in the past hundred years.