Knowledge management being implemented in organizations with low cost, less risk and less time is widely recognized to be one of the crucial problems. Using formal and informal methods we propose a description model to support knowledge management in an software organization with many projects and many people. The prototype system based on the model can help the organizations to capture, store and share knowledge produced by different people during different software development and avoid the repeated storage of the same knowledge package produced by different people or different project. The main ingredients of the model are: (1) meta-model and conceptual model of knowledge management, and (2) description of the knowledge management model. The model was implemented and evaluated empirically; the results suggest that knowledge management using requirements successfully promotes knowledge reuse.