Crop rotation affects dynamic changes of C factor in USLE and reduces hillslope soil erosion by improving soil properties. Based on six years observation data of runoff, soil loss and rainfall from the soybean-red adzuki bean rotation and bare-fallow runoff plots in the thin layer Mollisol region of the Northeast China, this paper analyzed erosive rainfall characteristics, discussed effects of crop rotation on preventing hillslope soil erosion, and explored yearly and monthly changes (May-October) of C factor (crop cover and management) during 2011-2016. The results showed that all erosive rainfall in the study area occurred from May to October, which occupied 32.5% to 68.1% of annual precipitation, and its distribution of inter-annual was uneven. For the bare-fallow runoff plot with 5° slope gradient, soil erosion mainly occurred in June to August and annual runoff and soil loss was 48.4 mm and 1 388.2 t/(km²·a) respectively; while for the crop rotation plot with 5° slope gradient, soil erosion mainly occurred in May to July and annual runoff and soil loss was 19.5 mm and 166.7 t/(km²·a) respectively. Compared with the bare-fallow plots, average annual runoff and soil loss from crop rotation plot under 5° slope gradient were decreased by 59.7% and 88.0%, respectively. Average yearly C value for crop rotation plots was 0.12. For soybean crop, C value was 0.04, ranging from 0.007 to 0.080; and for red adzuki bean, C value was 0.38, ranging from 0.28 to 0.46. Monthly C values of soybean and red adzuki bean varied between 0.01~0.24 and 0.01~0.80, respectively. The soybean-red adzuki bean rotation had a significant effect on preventing hillslope soil erosion in the thin layer Mollisol region of the Northeast China. The results provided scientific basis for quantitative evaluation of soil erosion and prediction model establishment in thin layer Mollisol region of the Northeast China.