Circulation Control (CC) is widely researched because it can generate high lift and create the effect of ‘virtual control surfaces’. Currently, the relationship between the design parameters and the control effects of circulation control is not yet clear. Therefore, this paper establishes the airfoil parametrization method for circulation control airfoils and the effects of different nozzle heights, radii and shapes of Coanda surface, and airfoil thickness and camber on circulation control effect are investigated. The results show that the best equivalent lift-to-drag ratio (K_E) is at a nozzle height of h/c = 0.06%; K_E peak at a Coanda surface radius of a/c = 0.016 and stabilize thereafter; the optimal Coanda surface shape is at b/a = 3/2. Increasing airfoil thickness and camber improves pitch moment but reduces K_E. The best overall performance is achieved at t/c= 15% and w/c= 0%.