This paper presents a new object oriented substation automation system model. The model is based on the IEC 61850 communication standard， and inherits the object oriented and layered characters of the IEC 61850 model. By the extension of logical device and logical node as well as the mirror node technology， the presented model extends the IEC 61850 model from communication model to integrated model in intelligent electronic device（IED） design. On this basis， this paper presents an IED software frame on layered platform， in which the developer can install different kinds of IED software by defining， configuring and organizing different logical nodes and logical devices.