knowledge-based system for querying reusable software components is presented in this paper. It supports object -oriented programming method. In this system,the authors used a semantic network model for knowledge represention, and provided a knowledge represention language, CKRL, for describing the features of the reusable components and the knowledge for querying. The authors provided three kind of ways for querying, or semantic net associate querying. condition querying, and components evaluating.