Abstract: After analyzing the resources of the system aberration in a four-pass amplification system,it was found that some aberrations which have main influenceon the energy concertration in the far field were caused by the off-axis transmission and tilt of lens.Firstly the influence of the lens tilt at different positions on the system aberration was analyzed with the commercial ZEMAX software.It concludes that the four-pass lens has main influence.Secondly the relation between the tilted angle of this lens and the aberration components was analyzed and compared based on the Fringe-Zernike polynomial.Finally experiments were performed to prove the study reasonable.The conclusion provides guidance to control the wave-front distortion of the output beams and optimize the design of the similar systems.