With the analysis of incident angle and system aberration of microlens array, which would affect the illumination efficiency of the optical system, the optical efficiency and illumination uniformity are optimized. The efficiency loss which is caused by large incident angle is minimized by varying the curvature radius of the free-form double-lens. Two spherical lenses are used as Fourier integrator after the microlens array to increase the system efficiency. The simulation result shows that the optical efficiency and illumination uniformity are 60.51% and 94.24%, respectively, which proves the feasibility of the theoretical analysis.