A two-fluid large-eddy simulation（LES），based on the Smagorinsky SGS stress model and particle kinetic theory，and unified second-order-moment two-phase turbulence Reynolds averaged Navier Stokes modeling（USM-RANS）were used to study backward-facing step gas-particle flowsThe instantaneous results gave the evolution of anisotropic two-phase turbulence structures and particle dispersion processesThe LES statistical results and USM-RANS modeling results of particle averaged velocity and RMS particle fluctuation velocity were in good quantitative agreement with the experimental resultsHence，the USMRANS modeling was basically validated by LESHowever，in the shear flow region，the peak values of the twophase velocity correlation predicted by LES were larger than those predicted by USM-RANS modelingIt implied that the LES and USM-RANS modeling remained to be further validated and improved.