Business rules are operational rules that business organizations follow to perform various activities. We summarize researches for business rule extraction from legacy system and find that the limitation of these methods is to use static slicing, because static slicing sometimes produces a large portion of a source program, especially for programs with array and pointer variable. This paper presents a method using dependence-cache slicing technique to extract business rules. The proposed approach has been implemented as a system and experimented with a number of programs. The finding shows that our proposed approach can greatly improve previous techniques in slice precision.