Aiming at the problems in the current emergency management GIS systems integrated with atmospheric dispersion models, such as low spatio-temporal resolution and without 3D terrain, a set of three-dimensional gas diffusion simulation methods was proposed based on the CALPUFF model. The three-dimensional spatio-temporal distribution data of the gas diffusion concentration was obtained through multi-layer calculations, and the Marching Cubes visualization technology was used to read and display the data, achieving the dynamic gas diffusion effect in three-dimensional space. “12·23” Kaixian blowout accident was used as a case study and the simulation was carried out to compare with the actual situation in two and three dimensions. The results show that the three-dimensional calculation based on CALPUFF model has higher accuracy of the magnitude and spatial distribution of gas concentration, and the three dimensional spatio-temporal dynamic simulation has high resolution and reconstruction efficiency, achieving a good visual effect. It can better express the gas leakage process and diffusion pattern and provide an important auxiliary decision-making means for emergency management.