This paper presents the study of induced drag of 3D Co-Flow Jet (CFJ) wing at cruise conditions with different aspect ratios. The simulated aspect ratios are 20, 10 and 5. The wings are formed by two CFJ airfoils, namely CFJ 1 and CFJ 2, both modified from NACA 6421 airfoil with the injection slot size and suction slot size of the CFJ 2 enlarged by 80% and 85% respectively compared with the CFJ 1. The baseline wings with the non-controlled NACA 6421 airfoil are also simulated for comparison at the same aspect ratios. A momentum coefficient Cµ of 0.03 and 0.04 are used at the cruise condition with optimum aerodynamic efficiency and productivity efficiency. The angle of attack (AoA) is fixed at 5◦, which produces the optimum aerodynamic for the two CFJ wings and the baseline wings. The simulations employ the validated in house FASIP CFD code, utilizing a 3D RANS solver with Spalart-Allmaras (S-A) turbulence model, 3rd order WENO scheme for the inviscid fluxes, and 2nd order central differencing for the viscous terms. The study indicates that the induced drag coefficient of CFJ wings is increased with the decrease of aspect ratio. However, the Oswald efficiency is also increased with decreasing aspect ratio. The CFJ wings have higher Oswald efficiency than the baseline wings with the same aspect ratio becasue the lift enhancement effect outperforms the induced drag increase. In other words, the CFJ wing is less penalized even though the lift coefficient is higher than the baseline wing. The CFJ wing always has substantially higher ratio of CL /CD than the baseline wing since CFJ reduces the pressure drag significantly. For the corrected aerodynamic efficiency of (CL /CD )c that includes the CFJ power consumption, the CFJ 2 wing’s result is slightly better than the baseline wing at aspect ratio of 20 and similar at aspect ratio of 10 and 5. However, attributed to the increased cruise lift coefficient, the productivity efficiency of the CFJ 2 wing measured by (CL2/CD)c is increased by 32.1% for the wing of AR 20, 19.4% for AR 10 and 5.6% for AR 5. For the power consumption comparison, the CFJ 2 wings at all aspect ratios have substantially lower CFJ power coefficient benefited from the larger injection and suction slot size. For the same momentum coefficient, the CFJ 2 wings with larger slot size have lower injection velocity, lower total pressure ratio between the injection and suction slot, and larger mass flow rate. The CFJ power coefficient is determined linearly by the mass flow rate, but exponentially by the total pressure ratio. Hence a decrease of the total pressure ratio has the major impact to reduce the CFJ power consumption. As a result, the productivity efficiency of the CFJ 2 wing is increased by 12.9%, 9.8% and 8.7% for AR 20, 10 and 5 respectively compared with the CFJ 1 wing. In conclusion, the CFJ wing is much more efficient than the baseline wing at either high or low aspect ratio. Furthermore, the CFJ power consumption can be substantially reduced by using large slot size with reduced injection jet velocity and jet total pressure ratio. This is particularly important for the same CFJ airfoil with fixed geometry to be used for whole flight envelop from takeoff to cruise and landing.