Abstract: It is of great value for the development of phototherapy equipment to improve the uniform distribution of illuminance on the irradiation plane of the light therapy light source composed of light emitting diodes (LED). An illuminance optimization method for phototherapy LED light source based on multi-objective artificial fish swarm algorithm was proposed, and designed two different combination modes of phototherapy LED light source array. Combined with multi-objective artificial fish swarm algorithm, the combination data of phototherapy LED light source array was optimized to make the illuminance distribution of phototherapy LED light source array more uniform. The optimized design of phototherapy LED light source chip combination data were imported into the optical simulation software TracePro to achieve simulation verification. The illuminance uniformity of the optimized circular light source arrangement is 0.104 higher than that of the un-optimized circular light source arrangement, and the illuminance uniformity of the rectangular light source arrangement is 0.148 higher than that of the un-optimized rectangular light source arrangement. By comparing and analyzing the final data, it shows that the optimization method is feasible and can improve the illuminance distribution level of phototherapy LED light source.