Based on the requirements of smart substation proposed by State Grid Corporation, such as simple architecture, module integration, software visibility, human-computer friendliness, this paper designs smart substation automation system from systemic and global perspective. Initially, we study the development trend of the smart substation automation system. Then the essay proposes the system structure and soft-ware structure of the smart substation automation system. The following part introduces the key technologies of monitoring system, network information security system, error prevention system as well as the configuration technologies and the visual editing of software logic. After that we have verified the application prospect and economic benefits through engineering experiment. In the last, the paper has analyzed the next stage work plan.