Objective To investigate the correlation of serum relaxin level with female pelvic organ prolapse (POP) and menopause. Methods Thirty-nine patients with POP (POP group) were selected, and another 39 women with normal pelvic floor function were served as control group. The relationship between POP and serum relaxin level was analysed, and the effect of menopause on serum relaxin level was investigated. Results The mass concentrations of serum relaxin in POP group and control group were (406.7±311.2) ng/L and (199.4±208.7) ng/L respectively, and there were significant differences between two groups (P<0.05). The mass concentrations of serum relaxin of menopausal women and non-menopausal women were (172.0±197.5) ng/L and (587.5±716.8) ng/L respectively, and there were significant differences between two groups (P<0.05). The mass concentrations of serum relaxin of menopausal women in POP group and in control group were (226.2±178.8) and (108.4±98.7) ng/L respectively, and there were significant differences between two groups (P<0.05). The mass concentrations of serum relaxin of non-menopausal women in POP group and in control group were (1870.2±264.4) ng/L and (373.7±370.4) ng/L respectively, and there were significant differences between two groups (P<0.001). Conclusion The elevation of serum relaxin level may be the cause of female POP.