Spatial metadata is defined as "data about spatial data". It records the descriptive information for spatial data, such as producing date, precision, spatial domain and so on. Recent progress on data retrieval technologies has made spatial metadata shared anywhere. However, different spatial metadata servers adapt different metadata system in backend. Metadata standards are quite different from each other as well. So to visit different metadata nodes users might have to use many different client tools. Z39.50 protocol is the information retrieval standard of ANSI/NISO. The protocol mainly specifies retrieval services and interactive details between client and server. It's widely used for eliminating the discrepancies between different systems. The authors implemented it to set up a SMSS (Spatial Metadata Service System), so users could visit any metadata server with SMSS by using one common client supporting Z39.50 protocol. Architecture of SMSS was derived in this paper, it mainly contains three parts: Z39.50 server, retrieval engine and metadata management. Key approaches for implementing them were presented as well. An actual SMSS was accomplished, use of which indicates that it provide an effective way for establishing a spatial metadata server.