Using k-ε turbulent equation and SIMPLE arithmetic, a multi-buildings space model was set up under realistic circumstances. The methane (CH4) leakage diffusions from 3 gas-transporting pipelines with different pressures under 3 different wind flow conditions in the space with multi-buildings were simulated and the simulation results were contrasted and analyzed. Simulation results indicate that the leakage diffusion of CH4 could be influenced by surrounding buildings, besides the effect of the wind flow. In addition, CH4 gassy columniation will be bended to be adsorbed by surrounding buildings forming a high concentration zone when the pipe pressure is rather low or the wind velocity is rather fast. It will greatly increase the fatalness to the ambience and surrounding buildings.