In regions prone to heavy snowfall, an accurate estimation of snow redistribution on roofs under the action of wind is vital for structural engineers. The content of unbalanced snow loads of flat roofs caused by snow transport is indispensable in current load codes/standards. Hence, the wind tunnel tests were performed to investigate the redistribution of snow on flat roofs, in which high-density silica sand was used. The characteristics of snow redistribution on flat roofs are discussed, and common features are pointed out. The largest snow depth usually occurs near the windward region, and for a large-span flat roof the peak point could also occur in the rear region of the roof. In addition the locations of peak points after snow redistribution and the influence of wind velocity, wind duration and roof span on transport rates and mass fluxes are analyzed in detail. The transport rate increases as wind velocity or roof span increases but it is not a simple proportional relationship with roof span. Moreover, the transport efficiency of particles declines as wind duration becomes longer. Mass flux of the entire roof, which is the transport rate per unit length, asymptotically decreases with the increasing of roof span.