Customer Relationship Management (CRM) has become one of the leading business strategies in 21 century. Because of CRM's complexity, little research has been conducted in defining and applying of CRM strategy. On analyzing the reason of the failure of CRM, which are the inexplicit strategy definition and the misidentification of key processes, resources, competences and technologies aligned with CRM strategy, we use Balanced Scorecard as a new tool to define Customer Relationship Management strategy. In the paper, we propose that BSC is one of the most suitable tools to describe CRM strategy, and a model for defining CRM strategy based on BSC is set up. At last, we illustrate the model through a case study to validate its feasibility and validity.