Strict secondary flow (suction and blowing) issued from two slots symmetrically placed at a distance y from the cylinder’s axis and embedded on the cylinder’s rear face has been used to numerically study the active control of flow past a square cylinder in a horizontal channel. We investigate the effects of the slots position y, blowing and suction intensity ui on the drag and lift coefficient variations and on the instantaneous wake structure. The findings indicate that blowing and suction both have the ability to lessen the frequency of vortex shedding and the varying lift and drag forces. The splitting of the circulation bubble into multiple vortices causes a drop in St values at low jet velocities. A bistable pattern is observed at y = 0.35, 0.40 and 0.45 for ui = 1.5 and 2.