The power dispatching automation system is widely used in power grid, a hazard or problem of power system will affect the security of power grid operation in a wide range. Software quality model of power dispatching automation system is built, and index system is proposed to evaluate software quality in this paper. Testing methods for indicators and comprehensive evaluation method are put forward, and then a comprehensive quality index is given, which improve the efficiency and accuracy of software evaluation. It provides a strong support for stable operation of power dispatching automation system and safe operation of power grid. Quality evaluation of state estimation, which is typical software of power dispatching automation system, shows evaluation method is feasible, and has a good value.