With a rapid growth of the Internet, exploring cost-effective and time-efficient methods for creating Internet services has become critical. As an emerging technology, service aggregation has been regarded as a promising candidate. However, it also raises serious issues on privacy management, as a service is usually provided by multiple providers that are usually transparent to its users. We observe that these issues have not been formally studied in the literature. In this paper, we propose a formal model for the privacy management in service aggregation and present a negotiation strategy on different privacy policies between two organizations.