The invention relates to a polychromatic illumination device of a plant incubator capable of realizing an LED polychromatic illumination function in a biological incubator. The polychromatic illumination device of the plant incubator comprises an LED driving circuit, a light intensity detection circuit, and a control module. The control module is used for control by adopting a minimum system of an MSP430F5529 single-chip microcomputer. The LED driving circuit is used to realize constant current working of an LED by adopting an LM3404 constant current driver. The light intensity detection circuit is used for detection by adopting a GY-30 illumination intensity sensor. A single-chip microcomputer control system is used to change the illumination intensity of the LED by adjusting an LED constant current driving circuit. Photosynthesis efficiency of cultivating the plant in the illumination incubator is improved, and the economic benefit maximization of the incubator is realized, and then the polychromatic illumination incubator is designed. By comparing with a common illumination incubator, the polychromatic illumination incubator is capable of greatly improving plant photosynthesis efficiency.