According to the feature of class, this paper defines strict class dependency and fractionates dependency into data dependency and method dependency, and proves strict and describes the two concepts. 对类之间的依赖关系进行严格的形式化定义和说明,并依据类的基本特征将依赖关系细分为:数据依赖、方法依赖,并对二者也进行了形式化定义和说明。