Abstract: This paper presents constructive principles and building approaches of grey system prediction models for soil gravity erosion in loess hills and gullies. With the models, the author made test research on soil gravity erosion in Wangjiagou watershed in Lishi County, west Shanxi Provence. And the relationships between prediction values of the models and observed values of soil gravity erosion are reflected with gray relational extents, and prediction precisions of the models are analysed. Meanwhile, to mirror the dynamic changing rules of soil gravity erosion system, the principle and approaches of the remnant distinguishing are introduced, so as to improve prediction level of the models. The models have high prediction precisions, and provide a new way of quantitative analysis for researches on soil gravity erosion in loess regions.