Abstract: Numerical simulation is an important method to study the spatial and temporal distribution of automotive dusting． The inflow concentration of dusting from the ground is one of the key boundary conditions for numerical solving． Unlike those existing concentration conditions with the overall uniform inflow intensity or the predefined local inflow intensity，the concentration expression of bed load according to the local flow field conditions was deduced． Based on this method，the effects of gravity and wheel rotation on dusting were investigated． The approximate exponential relationship between the automotive speed and the dusting amount was noticed． The present method will provide the positive effect for the further study of pollution caused by vehicles．