To detect the expressions of serum microRNA-155 (miR-155) and programmed cell death factor (PDCD4) of women with polycystic ovary syndrome (PCOS), and to explore its clinical significance. Methods: 128 women with PCOS in 19-25 years old were selected in study group and 60 healthy women in 19-25 years old were selected in control group from October 2015 to December 2019. The level of serum miR-155 of women in the two groups was determined by real-time quantitative PCR (qRT-PCR), and the expression of PDCD4 protein was detected by ELISA. Pearson method was used to analyze the correlations between the expressions of serum miR-155 and PDCD4 of women with PCOS and their indexes of obesity, lipid abnormality, and insulin resistance. Results: The levels of serum miR-155 and PDCD4 protein of women in the study group were significant higher than those of women in the control group (P＜0.05). In the study group, the levels of serum miR-155 and PDCD4 protein of women with insulin resistance were significant higher than those of women without insulin resistance, the levels of serum miR-155 and PDCD4 protein of women with obesity were significant higher than those of women without obesity, the levels of serum miR-155 and PDCD4 protein of women with abnormal lipid level were significant higher than those of women with normal lipid level, the levels of serum miR-155 and PDCD4 protein of women with insulin resistance were significant higher than those of women without insulin resistance (all P＜0.05). The levels of serum miR155 was positively correlated with body mass index, total cholesterol level, and insulin resistance index of women with PCOS (r=0.37, 0.47, 0.45, P＜0.05). And the level of serum PDCD4 protein was positively correlated with body mass index, total cholesterol level, insulin resistance index of women with PCOS (r=0.39, 0.46, 0.43, P＜0.05). Conclusion: The expressions of serum miR-155 and PDCD4 of women with PCOS are high, which are related to obesity, lipid abnormality, and insulin resistance of women with PCOS.