Intensity distribution of diode laser is not uniform due to the broad-area and ridge-waveguide designs, poor beam quality is the limiting factor of industrial applications. In order to achieve homogenized spot by beam shaping of high-power diode laser stack, a homogenization system for diode laser stack based on microlens array is designed. The diode laser beam shaping theory of microlens array is analyzed. The lower limit of clear aperture of microlens is confirmed by analysis of the impact of the diffraction of microlens edge on the spot homogeneity. The simulation and experimental test are carried out for the microlens array beam shaping system by a diode laser stack with 6 bars, realizing the spot with the homogeneity of 92.59% and energy utilization of 91.19%. The beam shaping system can be well used in diode laser welding, cladding, surface hardening and other industrial fields.