[Objective] Interrill erosion is a complex process triggered jointly by a number of influencing factors, and the effects of each factor vary with changes in other factors.[Method] Based on the data published and available in the literature and multiple linear regression analysis, the effects of soil type, rainfall intensity, slope gradient and slope length on interrill erosion process and the interactions were quantitatively analyzed.[Result] Results show that rain intensity, slope gradient, interrill erodibility and slope length were the main factors contributing to interrill erosion rate positively, and among the factors, rain intensity was the major one, contributing (62.93%). Analysis of the interactions between these factors shows that the increase in slope length promoted the contribution of the factor of slope gradient, but inhibited the contribution of the factor of rain intensity. The increase in slope gradient promoted first and then inhibited the contribution of the factor of slope length, but did reversely the contribution of the factor of rain intensity. The slope gradient of 20% was the inflection point of the interaction between slope length and rain intensity, changing from positive to negative. The increase in rainfall intensity interacted positively with slope length and slope gradient. However, slope gradient was more dependent on rainfall intensity than slope length.[Conclusion] During the process of interrill erosion, the interactions observed between the factors of soil type, rainfall intensity, slope gradient and slope length were either positive or negative. All the findings in this study are of great significance for revealing mechanism of rill erosion and predicting soil erosion on slopes.