Abstract: The visualization of power grid operation situation is an important tool for grid dispatching. However, the current browser/server architecture cannot meet the real-time visualization requirement due to the calculation burden of power system dynamics. To solve this problem, this paper proposes a dynamic visualization method of power grid security situation based on parallel rendering of multiple image layers, analyzes the feasibility and technical difficulties of the application of OffscreenCanvas to parallel rendering of multiple image layers, and designs a dynamic visualization method for several important security situation scenes. Combined with the characteristics of OffscreenCanvas and power system data, the data distribution mechanism of multi-graph layer and the data organization mode of view layer are studied. In the case study of 658-node power grid, the time-saving performance of the proposed multi-layer parallel rendering scheme is about 4 times of the traditional scheme, which provides an effective support for visualization of power grid situation.