Abstract: 【Objective】To evaluate the cold resistance effect of N-acetyl-D-glucosamineon on rice seedlings, and to further explore its potential cold resistance mechanism, with a view to providing the theoretical basis for the application of NAG in the field of agricultural immune induction.【Method】With the rice variety Nei 5 You 907 as the test material, different concentrations(0, 50, 100, 150 mg/L) NAG were exogenously applied to rice seedlings for root culture. The growth potential, growth index, chlorophyll content and soluble sugar content of rice seedlings under low temperature conditions were measured to characterize the cold resistance effect of NAG and to screen the optimum applied concentration. Furthermore, the cold resistance mechanism of NAG on rice seedlings was explored from osmotic adjustment system, root system, antioxidant system and abscisic acid metabolism pathways at the physiological and biochemical level.【Result】Exogenous application of NAG promoted the growth of rice seedlings in low temperature environments, and had obvious cold resistance effect. The optimum applied concentration was 100 mg/L. Under this concentration, the fresh weight(0.118±0.009 g), plant height(21.21±0.72 cm), root length(5.76±0.43 cm), soluble sugar(41.031±0.992 μg/g) and the total chlorophyll content(5.959±0.020 mg/g) of seedlings increased the most in comparison with the control group, which significantly increased by 14.14%, 7.14%, 7.22%, 63.09% and 36.79% respectively(P<0.05, the same below). The results of the physiological and biochemical level showed that 100 mg/L NAG promoted the accumulation of osmotic adjustment substances, soluble protein, proline, free amino acid in the cold injury seedlings increased significantly by 19.58%, 19.49%and 36.82% respectively compared with the control group;effectively protected the root system of seedlings, the root activity of cold injury seedlings was increased to 1.56 times, and the nitrate nitrogen content in the stem and leaf tissues was decreased by 15.65% compared with the low-temperature control group;effectively reduced the accumulation of malondialdehyde in the cold injury seedlings by 23.92% and increased the activities of superoxide dismutase(SOD) and peroxidase(POD) by 34.94% and 25.42% respectively, thereby protecting the antioxidant system of seedlings;increased the OsNCED, OsSDR and AAO genes expression in the abscisic acid metabolism pathway to 3.52, 1.73 and 1.64 times of low temperature control, so as to achieve the accumulation of endogenous abscisic acid in cold injury seedlings.【Conclusion】Exogenous application of NAG with root treatment can regulate osmotic adjustment system, root system, antioxidant system and the endogenous abscisic acid metabolism pathway of rice seedlings under cold stress, thereby improving the cold resistance of rice.