Based on the law of conservation of energy and the mesh generation method，the freeformsurface large angle lens was designed to achieve a nearfield uniform illumination of LED array, whose inner surface is elliptical, the outer is freeformsurface. According to the mapping relations established by the law of conservation of energy, the mesh generation of the light source and the target surface was realized. Then, the refraction law was combined with the iteration to solve the freeformsurface data points. We analyzed the influence of the short axis and long axis ratio of the elliptical inner surface on the lens Fresnel loss and uniform illumination. The researches show that it can be obtained a high light efficiency and an optimum uniformity of illumination when the ratio is in the range of 0.35~0.55. Through the feedback optimization method to optimize the LED array and redivide the grid , the light intensity superimposed part is weakened and the overall illumination uniformity is improved. The simulation results show that when the height of target plane is 80mm and light angle is 157°, the illumination uniformity can be increased from 0.40 to 0.84 after the optimization of the freeformsurface data points,and the efficiency is greater than 0.9.