以粗糙集理论中的上下近似集、属性约简、知识依赖度、属性重要度等概念为理论基础，将范例推理技术、相似系统相似度与粗糙集理论相结合，以云南37条泥石流沟的统计资料作为源数据，构建了基于粗糙集理论的泥石流危险度评价模型。提出了一种综合权重法计算影响因子的权值，利用范例相似度最大原则来探讨目标范例与源范例的关系。应用所建立的模型确定待评定的泥石流沟危险度等级，通过计算结果与实际值的分析比较，验证了危险度评价模型的可行性。

Debris flow is a kind of natural disaster extremely destructive to life and property, have such characteristics as outbreak in a short time, strongly damaging and simultaneous occurrence, etc. so, it is necessary to research debris flow hazard assessment. This article builds a risk assessment model of debris flow not only base on many concept of the Rough set theory such as upper and lower approximation, reduction of values, dependency graph of knowledge, but also base on case based reasoning, similarity degree of similarity system. In this hazard assessment model, basing rough set theory, the dada comes from statistical data of thirty-seven debris flow ditch of Yunnan. Proposing calculation method of synthesized weights to calculate the weight of impact factors, then sure the risk degree. By comparing the simulation results with those obtained consequence from the measured value, the risk assessment model is proved to be credible.