In order to obtain the rectangular beam required for liquid crystal display(LCD) repair technology with good beam quality and uniform energy distribution, a new beam shaping system has been proposed. In this system, related diffraction patterns can be obtained by calculating and analyzing the diffraction effects in theory at different positions through rectangular aperture, and a proper diffraction surface, which will be used to process the sample, can be extracted and transferred by using 4f image relaying system. In addition, a relevant experimental device has been designed to prove the feasibility of this system. The results show that there exit some of the complex diffraction patterns after passing through the aperture, and some diffraction planes with very good energy uniformity distribution can be selected in the 56.0~58.5 mm range of the equivalent distance. The effective delivery is achieved by the use of 4f imaging system, the fluctuation range of energy on the top of shaped beam is less than 5%, and energy efficiency is about 80%.