The key nodes of laser subsystems on the Shanghai Ultrafast Laser Facility are selected to measure the laser beam wavefronts, and then the origin, evolution, and causes of wavefront distortion are analyzed. Further, the effects of installation stress of optical devices and quality of Ti∶sapphire crystals on the wavefront are investigated. The results demonstrate that the laser wavefront distortion increases with the increasing number of large-aperture optical devices. Facet fabrication and installation and debugging errors of optical lenses are particularly important factors affecting wavefront distortion in a Ti∶sapphire laser amplifier. Such errors greatly affect the focusing ability of the laser. Measuring the wavefront of the laser system can help optimize and control the wavefront distortion of the entire system. In addition, such measurements can improve beam quality, focal spot properties, and focusing power density.