This work is represented to investigate a multi-pass scheme and its effect on both the phase matching condition and the pump beam depletion in a second-harmonic generation scheme. It is found that this arrangement is capable of enhancing the conversion efficiency through indirect increasing of effective interaction length which was reached by using consecutive reflections of the fundamental beam and its second-harmonic wave between two antiparallel mirrors embedded along both sides of the KTP nonlinear crystal. Such multi-pass scheme is simulated for the second-harmonic radiation of a pulsed Nd:YAG laser using a biaxial KTP crystal. By changing the angle between the mirror and the crystal axial, the output power of the second harmonic light is correspondingly computed. Finally, the range of polar and azimuthal angles for mirror rotation is simulated and the required graphs have been carried out from the results.