We aimed to investigate the risk factors for cervical intraepithelial neoplasia (CIN) in Jiexiu, Shanxi Province, China. Twenty thousand eligible married women (age: 18-65 years) were administered with a questionnaire on potential risk factors for CIN and underwent liquid based Pap test. All women with abnormal cytological results underwent colposcopy with biopsy. Based on the biopsy pathology results, women were then assigned to either study group (with CIN) or control group (negative for histological results and volunteered to participate in the follow up study). The women in both study group and control group underwent vaginal microflora detection and dietary survey. The potential risk factors were analyzed by using ordinal logistic regression. Among the 20,000 women ne 1,438 women (7.19%) had cytologic abnormalities and 410 (2.05%) women were diagnosed histologically with CIN lesions, including 317 (1.58%) with CIN1, 93 (0.50%) with CIN2/3and 11 (55/100,000) with squamous cell carcinoma (SCC). The average daily dietary folate intake was significantly lower in the study group (344.61±153.07μg) than in the control group (371.50±166.58μg; P<0.001). Multivariate analysis demonstrated that age of 56-65 years, farming as the husband's occupation, unwashing the vulva after sexual intercourse, and low self-reported folate intake were positively associated with CIN development and might have contribution to the increased CIN incidence in this population. These findings may provide help to develop the strategies to reduce the risk of cervical cancer in China.