An improved coupling method is proposed to ensure mass conservation in a previously developed DPM-CFD model (C.L. Wu et al., Three-dimensional discrete particle model for gas-solid fluidized bed on unstructured mesh, Chemical Engineering Journal 152 (2009), 514-529). In enforcing the mass balance for the continuous phase in such algorithms using the single phase flow solvers, any heterogeneity in the particle concentration field (caused by clustering of particles) creates non-zero source terms. It is shown that if this is not handled properly, it can create large numerical errors (of up to 10%) and any oscillation in the flow field manifests itself in a similar error in the mass conservation. By using the conservative form of the equations in integral formulation, the coupling between the DPM and CFD models ensures mass conservation on the global scale in the entire domain, even in the presence of local heterogeneities in the flow field. The method also offers a consistent implementation of mass flow boundaries at the inlet. Numerical results show the superiority of the new coupling method over the previous one in conserving mass and handling transport processes in fluidized beds. (C) 2011 Elsevier B.V. All rights reserved.