Abstract: The active control of two side-by-side cylinders wake with a Reynolds number of 4000 and a pitch ratio of 1.1 was studied experimentally by the Particle Image Velocimetry (PIV) technique. The flow has a bistable biased flow structure, and the biased gap flow leads to the asymmetry of the flow field. The vortex distribution and the lift spectrum of the cylinders wake were analyzed and it is found that the control effect of tangential jets on the wake can be divided into an invalid zone (θ≤20° or C_μ < 0.135), an incomplete zone (θ > 20° and C_μ > 0.135) and a complete zone (θ > 35° and C_μ > 0.304) according to the values of the jet angle and the jet momentum coefficient. In the incomplete zone, the induced tangential jets potential region can restrain the wake of side-by-side cylinders to a triangle region. The range of the vortex distribution decreases with the increase of the injection angle or the jet momentum coefficient, and the peak value of the lift force spectrum decreases gradually. In the complete zone, the wake of side-by-side cylinders is eliminated and no obvious vortex structure can be found in the time-averaged flow field, and the performance of tangential jets is at its best.