The SH-SY5Y cells were cultured in vitro and divided into control group，H₂O₂ group， melatonin groups， and N-acetyl-2-benzyltryptamine（Luzindole） group. The medium containing 200 μmol·L^－1 H₂O₂ was added in H₂O₂ group；different concentrations （1， 5 and 10 μmol·L^－1） of melatonin and medium containing 200 μmol·L^－1 H₂O₂ were added in melatonin groups； 50 μmol·L^－1 Luzindole， 10 μmol·L^－1 melatonin and the medium containing 200 μmol·L^－1 H₂O₂ were added in Luzindole group. The survival rates of human neuroblastoma SH-SY5Y cells were measured by CCK-8 method， the apoptotic rates of SH-SY5Y cells in various groups were detected by flow cytometry， and DCFH-DA fluorescence probe was used to detect the levels of reactive oxygen species（ROS） in the cells in various groups. The expression levels of microtubule-associated protein light chain 3-Ⅱ（LC3-Ⅱ）protein in the cells in various groups were detected by Western blotting method， and the fluorescence intensities of autophagic vesicles in various groups were observed by fluorescence microscope.

Compared with control group， the survival rate of SH-SY5Y cells in H₂O₂ group was decreased （P<0.01），the ROS level and the apoptotic rate were increased （P<0.01）. Compared with H₂O₂ group， the survival rates of SH-SY5Y cells in different concentrations of melatonin groups were increased（P<0.05），the ROS levels and the apoptotic rates were significantly decreased （P<0.01），the LC3-Ⅱ protein expression levels were significantly increased （P<0.01）， and the fluorescence intensity of autophagic vesicles in 10 μmol·L^－1 melatonin group was increased（P<0.05）. Compared with 10 μmol·L^－１ melatonin group， the survival rates of SH-SY5Y cells in 1 μmol·L^－１ melatonin group and Luzindole group were significantly decreased（P<0.05）；the ROS levels and the apoptotic rates in the SH-SY5Y cells in 1 and 5 μmol·L^－1 melatonin groups and Luzindole group were significantly increased（P<0.05），and the LC3-Ⅱ protein expression levels in the SH-SY5Y cells were decreased（P<0.05 or （P<0.01）， and the fluorescence intensities of autophagic vessicles in the SH-SY5Y cells in 1 μmol·L^－1 melatonin group and Luzindole group were significantly decreased （P<0.05）.

Melatonin can inhibit the H₂O₂-induced oxidative stress injury of SH-SY5Y cells and has a neuroprotective effect，and its mechanism may be related to reducing the ROS levels and enhancing the autophagy of cells.