A control volume analysis is given in this paper to analyze the jet effect on co-flow jet airfoil with injection and suction and the airfoil with injection only. The ducts reaction forces formulations to be included for lift and drag calculation are given. CFD solutions based on RANS model are used to provide the breakdowns of lift and drag contributions form the airfoil surface force integral and jet ducts reaction forces. The results are compared with experiment as validation. The duct reaction forces are also validated by a 3D CFD calculation of the complete airfoil with jet ducts and wind tunnel wall. A comparative study of the jet effect on airfoil performance between the CFJ airfoil with injection and suction and the airfoil with injection only is conducted. The study indicates that the suction occurring on the airfoil suction surface such as the CFJ airfoil is more beneficial than the suction occurring through the engine inlet such as the airfoil with injection only. For the airfoil with injection only, the drag actually acted on the aircraft, the equivalent drag, could be significantly larger than the drag measured by the wind tunnel balance because of the ram and captured area drag when the jet is drawn from the freestream. For CFJ airfoil, the drag measured by the wind tunnel balance is the actual 2D drag that the aircraft will be experienced. The CFJ airfoil does not have the ram drag and captured area drag. For a CFJ airfoil, the suction penalty is offset by the significant circulation enhancement. The CFJ airfoil with both injection and suction yields stronger mixing, larger circulation, more filled wake, higher stall angle of attack, less drag, and more efficient energy expenditure.