Ak-ɛ-PDF model based on statistical theory for turbulent gas-particle flows is proposed, and a numerical procedure combining the finite difference and finite fluctuating-velocity-group methods is used. The obtained statistically averaged equations have the same form as those obtained by using the Reynolds averaging. Using thek-ɛ-PDF model (PDF particle turbulence model combined with thek-ɛ gas turbulence model), many terms, such as the diffusion term in particle Reynolds Stress equations, can be accurately calculated for verifying the second-moment-closure model. Thek-ɛ-PDF model is used to simulate sudden-expansion particle-laden flow. comparison of the predictions using bothk-ɛ-PDF and thek-ɛ-kp models with experimental results shows that thek-ɛ-PDF model give more reasonable non-isotropic features of particle turbulence.