〔Abstract〕 Objective To investigate the effects of melatonin(MEL) on the proliferation of hepatic stellate cells(HSCs) induced by platelet-derived growth factor(PDGF-BB) and explore its correlation with the regulation of autophagy levels. Methods The HSC-T6 cells were divided into the following groups: control group, model group and MEL(low, medium and high) treatment groups. After 24 hours culture, the cells adhered to the wall and were changed into serum-free DMEM medium to synchronize the cells to the G0stage. After 24 hours culture, all groups were given with PDGF-BB(10 ng/ml) excepted the control group. Besides, melatonin of different concentrations(1 nmol/L, 1 μmol/L and 0.1 mmol/L) were added immediately in three treated groups. After incubated for 48 hours, the effect of MEL on the proliferation of hepatic stellate cells activated by PDGF-BB was detected by CCK-8 method. The protein expression levels of LC3b and α-SMA in hepatic stellate cells were determined by Western blot. The expression levels of LC3b mRNA and α-SMA mRNA in hepatic stellate cells were determined by qRT-PCR. The ultrastructure of HSCs was observed by transmission electron microscopy to understand the autophagy level. Results Compared with control group, PDGF-BB could induce the proliferation of HSCs(P<0.01). Compared with model group, MEL inhibited the proliferation of HSCs activated by PDGF-BB(P<0.01). Compared with the control group, LC3b and α-SMA protein expressions significantly increased in the model group(allP<0.05), and LC3b mRNA and α-SMA mRNA expressions significantly increased in the model group(P<0.05,P<0.01). Compared with the model group, MEL could inhibit such effects(LC3b:P<0.05,P<0.01; α-SMA:P<0.01). Transmission electron microscopy(TEM) showed that compared with the control group, autopolysosome significantly increased in the model group(P<0.05). Compared with model group, autopolysosome significantly decreased in MEL treatment group(P<0.01). Conclusion The up-regulation of autophagy level can promote the proliferation of hepatic stellate cells and the inhibition of hepatic stellate cell proliferation by MEL may be related to the down-regulation of autophagy level.