To increase the efficiency of planning the annual operation mode， an automatic computation and report generation system for the annual power grid operation mode is designed and implemented. By developing the database， the unified data platform of the operation mode is realized. Based on dynamic optimal allocation hardware， the multi-user and distributed parallel computation is adopted to do the huge computation of annual operation mode analysis. The functions of automatic computation according to workflow and report generation are performed. The structure， functions and key technologies are described. The application shows that the system can standardize the work of planning and analyze the annual power grid operation mode， thus improving the efficiency of power grid analysis.