Based on the SIMPLE-C algorithm and the non-overlapping Domain Decomposition Method (DDM), in which the Dirichlet-Neumann alternative algorithm is employed, a partitioning parallel procedure was developed to numerically simulate fluid flow in complex 3-D domains. It can well remove the limitation of speed and capacity of personal computer on large-scale numerical simulation of complex 3-D domains. In this paper, the 3-D turbulent swirling gas flow in cyclone separator was simulated. In view of the physical reality, the computational results are bascally reasonable.