The domain coverage method (DCM) is proposed to establish a computational fluid dynamics-discrete element method (CFD-DEM) model based on irregular mesh. The gas field was solved by Fluent software and the DEM model was coupled with Fluent software by user-defined functions. Gas turbulent viscosity was calculated by the coupled k-E two-equation model and the soft-sphere collision model was used to get particle contact force. The CFD-DEM model based on irregular mesh was firstly verified to be reasonable by comparing the simulated injected bubble with that simulated by Bokkers et al. The solid exchange behavior was studied numerically in a 2D dual-leg fluidized bed (DL-FB). The simulation results were compared with experimental results and proved that the CFD-DEM model is established successfully based on the efficient DCM. The DEM model is expanded to be used on irregular mesh in fluidized beds with complex geometries.