Objective: To investigate the role of microRNA-184 (miR-184) in polycystic ovary syndrome (PCOS) and to explore its potential mechanism. Methods: Fluorescence quantitative polymerase chain reaction (qRT-PCR) was used to detect the miR-184 expression in 24 cases of PCOS ovarian tissue specimens, 20 normal ovarian tissue specimens, human ovarian granulosa cells KGN and human normal ovarian epithelial cells IOSE80. The expression of miR-184 in KGN cells was inhibited by cell transfection. The proliferation of cells was detected by MTT assay. The ability of cell clone formation was detected by plate cloning assay. The p-p38 MAPK and p-ERK1/2 were detected by Western blot. The KGN cells of down-regulated miR-184 were treated with MAPK signaling pathway inhibitor SB203580 with a final concentration of 20 μmol/L, and the effect on cell proliferation was detected by the above method. Results: The expression of miR-184 was significantly up-regulated in ovarian tissue and KGN cells of polycystic ovary syndrome. Transfection of miR-184 inhibitor in KGN cells significantly inhibited the expression of miR-184. After down-regulating the expression of miR-184, the proliferation of KGN cells and the ability of cell clone formation were significantly decreased, and the expression levels of p-p38 MAPK and p-ERK1/2 protein in the cells were significantly decreased. Compared with the control group, the difference was statistically significant (P<0.05). Inhibitor SB203580 down-regulated miR-184 expression in KGN cells, and the cell proliferation and cell clone formation ability were significantly decreased, compared with the cells directly down-regulated miR-184, the difference was statistically significant (P<0.05). Conclusion: MiR-184 can promote the proliferation of ovarian granulosa cells, and its mechanism is related to the activation of MAPK signaling pathway, which provides a potential target for the treatment of PCOS.