Chooshing the Knowledge management strategy is affected by different organizational factors like business strategy, organizational structure, organizational culture, Information Technology strategy, human resource management, and dynamics of knowledge. It is difficult for strategists to consider all these factors in choosing appropriate KM strategy. In this research after presenting a six step methodology for KM strategy development, we designed a decision support expert system for supporting the process of knowledge management strategy development. This system has been implemented in three Iranian companies as a multi-case study. We used a questionnaire for validating the knowledge base and model base of the system. Furthermore, we compared the expert system results with the result of developing KM strategy without using expert system by analytical statistics techniques.