在大尺度空间中，仍然将整个空间划分上部热烟气层和下部的冷空气层直接进行区域模拟是不合适的。提出了一种将大尺度空间划分若干常规子单元，再在各个子单元中采用上下层区域模拟的方法，并以CFAST4.02为工具，对两种典型的大尺度空间的烟气运动过程进行分析和比较。结果表明，在大尺度空间中，这种多单元区域模拟的方法相比于传统的区域模拟方法具有较好的适用性。

In large scale building fire, it is improper to predict smoke descending using traditional simple two-layer zone model, which divides the total space of the building into upper hot smoke layer and lower cool air layer. In this paper, an improved method, named Cell-Zone Method, is used to solve this problem, which first divides the total space into some small subspaces and then uses traditional two-layer zone model in each subspace. Comparison is carried out between these two methods in fire smoke development simulation in typical large space buildings by CFAST4.02 software package. Results show that Cell-Zone Method demonstrates more applicability than traditional simple two-layer zone model in large scale building, especially in buildings having large scale in one direction.