Abstract: With the growing requirements of customized business, most existing business models fail to support tenant customizing in a simple and flexible way. So an ex-WSCL based SaaS (SaaS as a service) business-tenant model (exWSCL-SBTM) to describe SaaS business process was proposed. According to the characteristics of the model that the business process is organized by interactions and transitions, and according to the way that separate tenant end from business end, convenience and flexibility of multi-tenant business customization can be improved. On this basis, the definition of business customization operating behavior and business customization architecture based on SBTM were proposed.