As the world’s population continues to increase and land resources dwindle, traditional agricultural farming models are no longer able to meet the growing demand for agricultural products. Plant factories have been developed to address this issue. However, most plant light sources in plant factories have problems such as poor light uniformity and a single mode of light supplementation. To address these problems, this paper presents an intelligent light supplementation system with high uniformity and capable of spectral adjustment at different plant growth stages. The system uses an isotropic LED light source array with higher lighting uniformity and an STM32 microcontroller as the core for overall system design. The system can monitor ambient temperature and light intensity, change PWM output according to system preset values, and control the brightness of red and white LEDs by changing the current of the LED to achieve spectral adjustment. The test results show that the light uniformity of the light source reached 91.67% and the light source system was able to make precise changes according to the set light formula. This intelligent light supplementation system can be well applied in the field of plant growth lighting.