The fire design of semi-underground building is much strict according to the fire design of underground structure. Take the actual project of a Semi-underground building for example, evacuation distance of basement1 in this building over the standards. To solve the problem, the performance-based design uses the computer simulation to analyze the building. Using the simulated data judge the safety of the building. Then the paper gives advice of setting up the "Quasi safety zone" to solve the problem of evacuation distance. The paper discusses the fire safety of Semi-underground building and expects some advice to design of actual project.