In this paper, an off-axis two-mirror system that can not only make the output beam irradiance distribution uniform, but also control the output beam wave-front and beam-expansion ratio, is designed for laser shaping. By setting two constraints and initial conditions, the iterative relationship between the adjacent sampling points on the free surface can be obtained, and all the sampling points on the whole free surface can be calculated. We use a software to verify the system, and the 16 mm×16 mm square aperture is transformed into an 80 mm×80 mm square aperture and a 120 mm×20 mm rectangular aperture; the outgoing beams are all collimated beams. The results show that the square spot uniformity is 90.74%, and the beam expansion ratio is 5; the rectangular aperture spot uniformity is 94.75%, and the beam expansion ratios in the horizontal and vertical directions are 7.5 and 1.25, respectively.