The online monitoring system of smart substation equipment is an important unit in smart grid

which plays a vital role in guaranteeing the safety and efficiency of the power equipment. According to the design requirements for on-line monitoring software of smart substation

the database for the monitoring and diagnosis system of smart substation equipment was designed in this study. In this paper

the database design principles are explained

and the key technologies for database implementation are discussed. The expert system based on the designed database has been applied to the smart substation reconstruction project of Jining power supply bureau

and the application has proved that it is efficient and stable.