A domain-specific service registry should satisfy two requirements at least: coping with diverse service description requirements from different services; supporting semantic description on service interfaces for interoperation in a specific domain. This paper proposes an adaptive metadata model that supports flexible semantic description of service interfaces. It uses a simple inheritance mechanism to provide multiple metadata models on a light-weight generic metadata model and semantic annotation templates to facilitate interface semantic description for domain-specific services. The implementation and application of this metadata model in a real-world domain-specific service registry promises that a user can customize a metadata model and add interface semantic metadata in an easy-to-use way.