Abstract: In this study, a solid stress model that can be used in both dilute and dense regimes for simulation of gas-particle flows with comprehensive considerations of friction and the effect of local solid volume fraction gradient is proposed. In the dilute regime, solid stress is closed by a modified kinetic theory that accounts for the effect of particle friction and volume fraction gradient. In the dense regime, solid stress is closed by the inertial number model. The transition from dilute to dense regimes is realized by using a dimensionless parameter χ, which is a function of the inertial number Is. This new model is validated with experimental data and discrete particle simulation from spout-fluid bed and bubbling fluidized bed. When compared with the traditional kinetic-frictional stress model, this new model improves the transition from dilute to dense regimes and the particle velocity predictions in both beds.