Abstract: To study the transonic buffet that limit the flight envelope of both transporters and airliners, numerical simulations are conducted to investigate the effect of tangential slot blowing based on Venturi nozzle for both transonic buffet onset incidence angle and buffeting load. The results show that, tangential blowing from slots on the upper surface of airfoil can increase the onset incidence angle of transonic buffet, while it can greatly increase lift when the incidence angle is near and above the buffet onset angle; for different incidence angle in buffet state without blowing, numerical simulations for blowing slots at different span-wise locations with different total pressure ratios are carried out. The results indicate that, in case of tangential blowing at upstream of shock wave, the shock wave oscillation is depressed, thus the buffeting load is greatly reduced and the mutual-interference in-between the two separation bubbles downstream of shockwave is evidently weakened, inducing the high-frequency low-energy lift oscillations. At this blowing location, the buffeting loads are not sensitive to the blowing pressure ration. For blowing slots located at the mean and downstream locations of shockwave without blowing, the buffeting loads are not efficiently suppressed.