OBJECTIVE: To assess sexual activity, sexual function, and their correlation with vaginal maturation status among middle-aged Chinese women. METHODS: A cross-sectional study with comparisons across age groups was carried out. In all, 120 women aged 45 to 60 years were recruited into three groups: 45 to 50 (youngest group), 51 to 55 (intermediate group), and 56 to 60 years old (eldest group). Sexual function was assessed through the Female Sexual Function Index (FSFI); vaginal maturation status was determined through the Vaginal Maturation Index (VMI) and pH value. Sexual activity was recorded with self-administered questionnaires. RESULTS: Low sexual frequency was present in a higher proportion of women, but sexual distress was identified within a lower proportion of women in the eldest group. The total FSFI score was significantly lower in the eldest group than in the youngest and intermediate groups (P < 0.01 and 0.05, respectively); however, the domain score of sexual desire, arousal, and satisfaction was lower in the eldest group than in the youngest group (P < 0.01, 0.05, and 0.05) only. The domain score for lubrication was lower in the eldest group than in both the youngest and intermediate groups (P < 0.01 and 0.05), and the pain score was lower in both the intermediate and eldest groups than in the youngest group (P < 0.01 and 0.05). A lower VMI (P < 0.001) and a higher pH value (P < 0.01) were observed in the eldest group, compared with the youngest group. Moreover, VMI was positively correlated with the total FSFI score, the domain score for sexual desire, and lubrication (r = 0.26, 0.25, 0.34; P < 0.05, 0.05, 0.01), but the opposite associations were demonstrated for pH value (r = -0.47, -0.37, -0.38; P < 0.01, respectively), especially with vaginal pain (r = -0.44, P < 0.01). CONCLUSIONS: Among middle-aged Chinese women, sexual desire is lower in 56 to 60-year-old women, compared with those aged 45 to 55 years, whereas vaginal dryness and dyspareunia become more prevalent with age. Importantly, sexual function is associated with vaginal maturation status in women at midlife.