Global optimization algorithm was proposed to optimize and design LED array for generating uniform illumination distribution on target plane. An evaluation function reflecting illumination uniformity was constructed, which can reach the minimum by optimizing the LEDs positions. While the evaluation function takes the minimum value, the optimal LED array can produce highly uniform illumination distribution on target plane. The minimum value of evaluation function was found by simulated annealing algorithm, so that the circular array consisting of 12 LEDs, 4×4 and 4×5 rectangular LED array were optimized. After optimization, the three arrays produce highly uniform illumination distribution with the calculated uniformity 97%, 96% and 95%, respectively. The results show that the optimal radius of circular array does not depend on the number of LEDs.The optimal radius depends linearly on the distance between LED array plane and the target plane. For the rectangular array, the optimal separation between adjacent LEDs depends linearly on the distance between LED array plane and the target plane.The results of the proposed method were consistent with existing method, and the algorithm is simple and convenient.