As a newly software delivery model, software as a service, SaaS for short, is the best way for small and medium enterprise to adopt the newly technology. However trustworthiness is greatest challenge in the wide acceptance of SaaS. In the absence of trustworthiness in SaaS applications, data privacy is the primary and the most important issue for tenants. How to protect the data privacy when software service and database are both hosted at the service provider's client is still an open issue. So based on the customization feature of SaaS applications and shared database shared schema storage model, this paper demonstrates the shared data storage model, defines three kinds of privacy constraints, and then proposes a customizable privacy constraints based approach for data privacy preserving by combing data encryption and information disassociation. This approach is proofed correctly and could be used for privacy preserving in SaaS applications in static scenarios.