This paper studies the lift enhancement using Co-Flow Jet (CFJ) active flow control for circular cylinders with Reynolds number of 3 × 106. For potential flows of a circular cylinder, the maximum lift coefficient limit is derived as 4π. The present study indicates that the zero-net mass-flux CFJ active flow control is able to achieve the maximum lift coefficient that far exceeds the theoretical limit. The present research is based on validated CFD simulation, which employs 2D RANS solver with Spalart-Allmaras (S-A) turbulence model, 5th order WENO scheme for the inviscid fluxes, and 4th order central differencing for the viscous terms. The momentum coefficient Cµ studied is from 0.2 to 0.8 and different CFJ injection and suction slot configurations are varied for parametric trade study. The super-lift coefficient of 28 is obtained at the jet momentum coefficient of Cµ = 0.8. The flow filed around the cylinder is attached by the strong circulation between the injection and suction. The stagnation point is detached from the surface by the dramatically increased circulation.