In accordance with the characteristics of soil erosion of small watershed in the loess plateau, the problem on building the soil erosion model system was analyzed. Firstly, the processes of the soil erosion model were described.Secondly, the development of the soil erosion model was discussed, the two modelty pes were compared,and the structure of the distributed parameter model spatially and temporally were designed and analyzed. Lastly,many merits of the distributed parameter model system were indicated, which reflected the development trend of the present soil erosion research.