It is an important function to provide data discovery, access and retrieval service in the WMO Information System (WIS). In recent years, the OAIPMH protocol is widely used in data sharing and the metadata synchronization field because of its simplicity, openness and operability. After a brief introduction of the OAIPMH protocol, the design of the metadata synchronization function of WIS is presented. The design is composed of metadata repository, metadata provider service, and metadata harvester service. Then the work flow of metadata provider and harvester service is discussed in detail. The metadata synchronization function is developed using Java language. The provider service has passed the testing of the open source software OAI (Open Archive Initiative) and JOAI (Javabased OAI) official website, and the harvester service has successfully harvested the metadata of DLESE （Digital Library for Earth System Education） and the Climate Data Center of Deutscher Wetterdienst.