Objective To detect the levels of sex hormones and insulin in follicular fluid（FF） and the expression level of phosphatase and tensin homolog deleted on chromosome ten（PTEN） in granulosa cells in the infertile patients with polycystic ovary syndrome（PCOS）， and to preliminarily explain the correlations between the insulin level and the expression level of PTEN mRNA. Methods Seventy infertile patients were selected as the subjects and divided into PCOS group and control group （tubal obstruction or infertility due to male factors） according to infertility factors. All patients received in vitro fertilization-embryo transfer（IVF-ET） treatment. FF and ovarian granulosa cells were collected on the day of ovulation. The expression levels of PTEN mRNA in ovarian granulosa cells of the patients in two groups were detected by real-time fluorescence quantitative PCR（RT-qPCR） method. The levels of sex hormone and insulin in FF were measured by electrochemiluminescence. The correlations of the PTEN mRNA expression level in ovarian granulosa cells and testosterone（T） in FF with the level of insulin in FF were analyzed by Spearman correlation analysis method. Results There were no significant differences in age， infertility years， body mass index （BMI）， basic sex hormone， total dose of gonadotropin（Gn） and days of ovulation induction in two groups（P>0.05）. Compared with control group， the anti-Mullerian hormone（AMH） and antral follicle counting（AFC） of the patients in PCOS group were significantly increased（P<0.05）. The RT-qPCR results showed that the PTEN mRNA expression level in ovarian granulosa cells of the patients in the PCOS group was higher than that in control group（P<0.001）. The electrochemiluminescence results showed that the levels of T and insulin in FF of the patients in PCOS group were higher than those in control group（P<0.05）， whereas the estrogen and progesterone levels were lower than those in control group（P<0.05）. The Spearman correlation analysis showed that that T level in FF was positively correlated with the insulin level of the patients in PCOS group（r=0.577， P<0.001）， and the PTEN mRNA expression level in ovarian granulosa cells was positively correlated with the insulin levels in FF （r=0.616， P<0.001）； in control group， there was no correlation between T level and insulin level in FF（r=0.266， P=0.123）， and there was no correlation between the expression level ofPTEN mRNA in granulosa cells and the insulin level in FF in control group （r=-0.214， P=0.216）. Conclusion The high expression of PTEN in granulosa cells of the infertile patients with PCOS may be related to the local hyperinsulin level in the ovary， and PTEN participates in the occurrence and development of PCOS.