Existing plant light source systems do not provide a sufficiently high-quality lighting environment for optimal plant growth, the theory of spatial illumination uniformity is proposed. The plant light source system with multiple light source modules is adopted to achieve high spatial illumination uniformity and color-mixed uniformity in the plant growth space. The multi-light source module is composed of inverted light source, straight down light source and central light source in the growth space. The experimental process is simplified according to the Taguchi theory and the key factors are optimized in conjunction with an analysis of varianceto find the optimal plant light source system. The shape and spacing of LED beads are further optimized to obtain a three-dimensional plant light source system with the illumination uniformity of horizontal and vertical planes of 91.35% and 89.71%, and color-mixed uniformity of 87.67% and 88.54%, respectively. Plant growth is simulated and tested in kind, the experimental results show that the three-dimensional plant light source system can provide high-quality lighting effects for the entire plant growth space.