Abstract: In the laser parameters systems of big science projects, the installation errors of the shrink- beam system were analyzed. The result shows that the defocus between the objective lens system and the eyepiece system affects the wavefront distortion error of the system most. Besides, the PV values of the wavefront aberration caused by the defocus between the objective lens system and the eyepiece system of the shrink-beam system were analyzed and a conclusion that there was a non-linear relationship between the PV values and the defocus was drawn. By the test system composed of large aperture long focal length collimator, fiber lasers and Hartmann wavefront sensors, the wavefront aberration of the laser shrink-beam system was measured and verified real-time. The result shows that by wavefront computer- aided technology, the PV values of wavefront aberration can be less than 0.2(=1.053 m).