Objective To observe the effects of resveratrol on the proliferation and apoptosis of ovarian granulosa cells（OGCs） and the changes in the morphology and function of mitochondria in a rat model of polycystic ovary syndrome（PCOS）， and explore its possible protective mechanism. Methods Thirty-two young female Sprague-Dawley rats were randomly divided into two groups：polycystic ovary syndrome model group（n=24） and model control group（n=8）. Granulosa cells were extracted from the PCOS group and cultured in vitro，and treated with different concentrations of resveratrol. CCK-8 assay was used to measure the changes in cell activity； Mito Tracker Deep Red staining was used to observe the morphological changes in cell mitochondria；JC-1 was used to measure the changes in mitochondrial membrane potential；ATP kits were used to determine the changes in ATP content；spectrophotometry was used to measure the changes in enzymatic activity of caspase-3 and caspase-9，which are closely associated with apoptosis；finally，Western blot was used to measure the changes in the levels of caspase-3 and caspase-9 proteins. Results After treatment with resveratrol， the OGCs in the rat model of PCOS showed a significant increase in proliferation activity（P=0.000）. Mito Tracker Deep Red staining showed a significant increase in mitochondrial mass， with tubular or elongated shapes observed. ATP production and mitochondrial membrane potential in granulosa cells also significantly increased（both P=0.000）. In addition， resveratrol reduced the enzymatic activity and protein expression of caspase-3 and caspase-9（both P=0.000）. Conclusion Resveratrol inhibits the apoptosis of OGCs and promotes cell proliferation in the rat model of PCOS，which is associated with the improvement of mitochondrial morphology and function of granulosa cells by resveratrol.