To study the aerodynamics of sand fences, the mean velocity field around porous fences was simulated in wind tunnel based on the PIV technology, and its velocity decrement effect was analyzed and evaluated. The results show that porosity has distinct effect on the mean velocity field, the lower the porosity the faster the mean wind velocity decreased. The vertical velocity component decreases with increasing porosity and shows the maximum value on the top of the fence, and it have potential influence on sand particles sediment transport process by alternating its saltating height. The total reduction coefficient of the mean wind velocity behind the fence can be fitted with a Gaussian peak function with the peak value at η =0.2, which represents the theoretical optimal porosity in terms of wind velocity reduction.In order to study the aerodynamics of sand fences, the mean velocity field around porous fences was simulated in wind tunnel based on the PIV technology, and its velocity decrement effect was analyzed and evaluated. The results show that porosity has distinct effect on the mean velocity field, the lower the porosity the faster the mean wind velocity decreased. The vertical velocity component decreases with increasing porosity and shows the maximum value on the top of the fence, and it have potential influence on sand particles sediment transport process by alternating its saltating height. The total reduction coefficient of the mean wind velocity behind the fence can be fitted with a Gaussian peak function with the peak value at η =0.2, which represents the theoretical optimal porosity in terms of wind velocity reduction.