In order to support the online real-time monitoring, control and analysis of large power grid, this paper proposes a new topology analysis method for large power grid based on graph partitioning. According to the model characteristics of the smart grid dispatching and control systems, this method first provides the power grid model of hierarchical structure, topology structure, the bus of substation analysis and system network topology. Then it establishes mathematical model for parallel network topology and local topology modification based on graph partitioning. According to this model, the realization method of the large power parallel topology analysis is designed. Finally using shared memory programming model, the function of the large power fast topology analysis services is developed in the smart grid dispatching and control systems. The models and method proposed realizes the no lock computing of large power grid parallel topology analysis, and avoids the blocking time-consuming problem caused by multithreaded data competition. Simulation is carried out by taking the actual power grid as an example, the veracity, feasibility and practicality of the proposed method are verified. This work is supported by Science and Technology Project of State Grid Corporation of China (No. KY-SG-2016- 031-JLDKY).