This paper deals with application requirements of seamless communication between smart substation and control center， especially model harmonization between IEC 61850 and 61970. The necessity and feasibility of IEC 61850 proxy server acting as a communication gateway in substation is introduced. It also describes software design of functions and architecture for proxy server. The proxy server makes full consideration of the application technologies of IEC 61850 and 61970， such as modeling methods， configuration tool， real-time database， IEC 61850 abstract communication service interface（ACSI） client， services mapping， access security， maintenance and hardware. The proxy server features perfect functions， simple configuration and easy maintenance， and will become an important front-end communication device in future construction of smart substation， providing technological support for seamless connections between heterogeneous systems in smart grid.