An application based on the Service-Oriented Architecture (SOA) consists of an assembly of services, which is referred to as a composite service. A composite service can be implemented from other composite services, and hence, the application could have a recursive structure. Securing an SOA application is an important nonfunctional requirement. However, specifying a security policy for a composite service is not easy because the policy should be consistent with the policies of the external services invoked in the composite process. Therefore, this paper proposes a security policy composition mechanism that uses the existing policies of the external services. Our contribution is defining the process-independent policy composition rules and providing a method for semiautomatically creating a security policy of the composite service. Our method supports two approaches of policy composition: top-down and bottom-up. Our study makes it possible to verify the consistency of the policies without increasing a developer's workload, even if the composite service has a recursive structure. © 2011 IEEE.