This paper concerns with building a knowledge-based application generator. For this purpose, we propose a knowledge-based reuse approach and this approach is applied to generate a capital management system written in dBASEIII. The knowledge-based reuse approach combines the concept of knowledge engineering and primitive patterns which are basic units of reusable software. The role of knowledge can be categorized into three parts according to the major steps of programming: specification, formalization, and implementation step. Each part constructs a unique knowledge base with its own knowledge representation. Primitive patterns are used in implementation step and domain knowledge is used in specification step to minimize user``s burden of specification. This study is applied to a capital management system, named TCM, developed in KAIST. Prototype of TCM generator illustrates knowledge-based reuse approach by generating some program modules of TCM.