Abstract: Different concentrations of 5-aminolevulinic acid (ALA) (100, 150, 175 mg·L^-1) were used to treat the three-year-old Zaozhong No.6 loquat container seedlings under the stress of low temperature. With spraying water as the control (CK), the effects of different treatments on the contents of hydrogen peroxide (H₂O₂), ascorbic acid (AsA) and reductive glutathione (GSH) and the activities of dehydroascorbate reductase (DHAR), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and ascorbate peroxidase (APX) in the leaves of loquat were compared and analyzed when applying the low temperature stress at -3℃ for 3 h. The results showed that:compared with CK, the exogenous treatment with ALA on the leaves of loquat significantly promoted the increase of the contents of ascorbic acid (AsA) and reductive glutathione (GSH), and the activities of dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR), glutathione reductase (GR) and ascorbate peroxidase (APX) in loquat leaves, but reduced the content of hydrogen peroxide (H₂O₂). This indicated that the exogenous treatment with ALA promoted the effective circulation of AsA-GSH in loquat leaves under the stress of low temperature, enhanced the antioxidant activities of cells, and improved the cold tolerance of loquat seedlings. Therefore, the appropriate exogenous treatment with 5-aminolevulinic acid (ALA) could regulate the AsA-GSH circulation in loquat leaves, thus improving the cold resistance of loquat leaves and reducing the damage of loquat under the stress of low temperature, among which the treatment with 175 mg·L^-1 ALA had the most significant effect.