Abstract: The application of traditional risk assessment theory in practical engineering has such problems as hard identifying system key information, considering little factors, insufficiently reflecting assessment detail and the evaluation time lagging. In this paper, due to the drawbacks in application of risk assessment theory, a grading assessment system of multidimensional risk is proposed from three dimensions of time, space and evaluation standard, based on which a multidimensional operation risk assessment system for power grid is developed. The concept and procedure of multidimensional risk grading and evaluating system are elaborated, and the software architecture, functional architecture and characteristics of risk assessment system are designed and introduced. In the end, the application of proposed system in Anhui power grid is given.