In order to realize the development and utilization of large-scale wind power, it is necessary and urgent to carry out the corresponding simulation research on large-scale wind farm. Due to the large and complex modeling of wind farm, the existing modeling methods adopt equivalent processing to wind farm with single machine or multi-machine. The equivalent model is small, the order of state space equation is low, and it is easy to simulate. However, there are problems such as low accuracy, poor flexibility and weak applicability of the model. In view of this, this paper proposes a full-topology real-time simulation method for large-scale wind farms. The main principle of this method is the combination of model segmentation method and parallel processing technology. To verify the effectiveness of the proposed method, a self developed real-time simulation platform (UUREP-300) is used to simulate an offshore wind farm in real time. Simulation results show that the proposed method can effectively reduce the computational and storage burden of the simulator, and greatly improve the simulation speed and scale, and can achieve the full topology real-time simulation on large-scale wind farms.