In order to obtain the matching criterion on optimal blowing momentum coefficient near the stall angle of attack for the tested airfoil model, the WA-A210 airfoil with sidewall boundary layer blowing control was tested in NF-3 wind tunnel. A special data processing method was used by subtracting the acquired pressure data in the same station between middle section profile and side section profile on airfoil surface, and the best blowing momentum coefficient can be obtained in different state on airfoil model. The results show that it can judge two-dimensional flowing state on the surface of airfoil by using the rule from this data processing method, sidewall blowing control can improve two-dimensional flowing on the surface of airfoil and decrease the effect of sidewall boundary layer on the airfoil experiment result.