Abstract: Objective Based on the CA model of rill erosion,the research was focused on the effect of different si-zes of cells on the process and characteristic parameters of rill erosion on loess hillslopes as well as theavailability of a CA model through the Nash-Sutcliffe coefficient Ensand error coefficient Refor cumu-lative runoff and erosion.The results show:when other parameters of model and the running time areunchanged,if the size of cell becomes bigger,the process of rill erosion will accelerate,the averagewidth of the rill will get wider,the length will get longer,the trend of runoff and erosion will ad-vance,and at the same time,the cumulative runoff will decrease and the cumulative erosion will in-crease.If the size of cell becomes smaller,the effects will be reversed.In addition,the velocity of theCA model depends on the ratio of cell length and time step and the effectiveness of the model can beimproved when it is closed to overland flow velocity.