Abstract: In order to explore the effects of different lights on seed germination, total flavonoids synthesis, and related enzyme activities of Toona sinensis seedlings, LED were applied to the seeds and seedlings of Toona sinensis. The experimental materials were ‘Hongyou Toona sinensis’. White light (CK), blue light (B), red and blue light 2:1 (R2B1), red and blue light 1:1 (R1B1), red and blue light 1:2 (R1B2), red light (R) were used for 15 days respectively, and the seed germination, total flavonoid synthesis and related enzyme activities in seedlings were measured. The results showed that compared to the control group (CK), the red light dominated illumination (R, R1B1, R2B1) promoted the seeds germination, and the dry and fresh weight of the whole plant treated with light (R2B1) increased by 55.06% and 82.86% respectively, which were the highest among all the treatments. Compared with CK and R, other light treatments significantly increased the total flavonoid content in Toona sinensis seedlings (P<0.05). Treatment B was significantly higher than other groups, and the activities of phenylalanine ammonia lyase (PAL), chalcone synthase (CHS), and chalcone isomerase (CHI) were also significantly increased (P<0.05), which showed a significant positive correlation with the changes in total flavonoid. Therefore, the germination of Toona sinensis seeds can be facilitated by the treatment of R2B1, and a significant enhancement in total flavonoid synthesis can be achieved by the treatment of B for Toona sinensis seedlings, effectively promoting the activities of PAL, CHS, and CHI enzymes.