The traditional plant lighting design only evaluates the uniformity of a single reference surface, and it is difficult to meet the light intensity and light quality requirements of different stages of plant growth. Aiming at this problem, first, a space lighting uniformity evaluation system was proposed, and based on this system, a three-dimensional lighting system with a composite light source module was proposed, in order to construct a plant lighting space with uniform lighting. Further, the Taguchi method was used to optimize the experimental process, and the optimal structural parameters were obtained on the basis of ANOVA analysis. Finally, the lamp beads shape analysis and the lighting effect test during the plant growth process were performed on the obtained optimal solution. The experimental results show that the optimal structure can provide a uniform illumination space with horizontal reference plane illumination uniformity of 87.22%, color mixing uniformity of 90.11%; vertical reference plane illumination uniformity of 93.02%, and color mixing uniformity of 91.43%. The plant light source system can meet the requirement of a uniform space lighting environment during plant growth.