Abstract: The paper investigated the responses of rice (Oryza sativa L.) seedling parameters (plant height, root length, and fresh and dry weight) and physiological characteristics (endogenous hormones, antioxidant enzymes, soluble protein and malondialdehyde) to the different light quality of supplemental light-emitting diodes (LEDs), and their after-effects on the grain yield.Rice seedlings were nursed at 1 000 μmol(photons) · m^-2 · s^-1 in a greenhouse with 30 day continuous supplemental lighting (6 h · d^-1) from different light sources, including no supplemental light (CK), 100% red (R), 100% blue (B), 80% red + 20% blue (RB), 62.5% red + 25% blue + 12.5% green (RBG_12.5) and 50% red + 25% blue + 25% green (RBG₂₅), and then were transplanted into paddy field.The results showed that the plant height, root length, fresh and dry weight of rice seedlings were significantly (P < 0.05) varied with the supplemental light sources.The highest plant height and the greatest aboveground dry weight were presented in R and RBG_12.5, respectively, while the longest root length and the greatest belowground dry weight were observed in RBG_12.5.Additionally, the physiological characteristics, including endogenous hormone, antioxidant enzyme, soluble protein and malondialdehyde of rice seedling were significantly (P < 0.05) influenced by the supplemental light sources.Among all supplemental light sources, RBG_12.5 significantly(P < 0.05) increased the content of auxin (IAA) and soluble protein, and B significantly (P < 0.05) increased the content of superoxide dismutase (SOD), peroxidase (POD) and malondialdehyde (MDA) in the aboveground parts.Compared with CK, RBG_12.5 and RBG₂₅ significantly(P < 0.05) increased the content of IAA, and RBG₂₅ significantly(P < 0.05) increased the content of soluble protein and MDA in the belowground parts.The effect of supplemental light sources on rice yield was consistent with that on rice strong seedling index, which was decreased in the order of RBG_12.5>RBG₂₅>RB>B>R>CK.Stepwise regression analysis showed that strong seedling index was positively related to the content of gibberellic acid (GA₃) and IAA in the aboveground parts and the content of SOD and IAA in the belowground parts.Rice yield was positively related to the content of IAA in the aboveground parts and the content of IAA and catalase (CAT) in the belowground parts.In general, the responses of rice seedlings to LED supplementary lights were regulated by the changes in physiological characteristics, which can extend to the rice maturity period, leading to corresponding changes in the grain yield.Among all supplemental light sources, RBG_12.5 was the most suitable supplemental light for rice factory seedling nursing.