Abstract： Objective To investigate the possibility of detection of the human papillomavirus (HPV)L1 capsid protein to predict the coarse of mild or moderate cervical intraepithelial neoplasia(CIN).Methods Immunocytochemical analysis using antibody against HPV L1 capsid protein was carried out on 274 samples obtained from women performed Tri Path Pap tests.positive for high-risk HPV DNA detected by hybrid capture Ⅱ (HC-Ⅱ)or cytologic diagnosed atypical squamous cells of undetermined significance (ASCUS)or more severe.For cytological diagnosed,there were ASCUS 105 cases,low-grade squamous intraepithelial lesions (LSIL) 119 cases,atypical squamous cells cannot exclude high-grade squamous intraepithelial lesion (ASC-H)9 cases,high-grade squamous intraepithelial lesions(HSIL)36 cases,and squamous cell carcinoma(SCC)5 cases.But for the pathologic diagnosed,there were chronic cervicitis 96 cases.CIN Ⅰ 55 cases,CIN Ⅱ 55 cases,CIN Ⅲ 32 cases,and SCC 6 cases.Results Of the 274 cases,HPV L1 capsid protein was positive in 69.8%(67/96) of cervicitis,83.5%(71/85)of CIN Ⅰ,41.8% (23/55)of CIN Ⅱ,3.1%(1/32)of CIN Ⅲ and 0(0/6)of SCC.Cytologic diagnosis revealed a higher expression rate in LSIL(75.6%.90/119) than that in ASCUS(63.8%,67/105)or in HSIL + SCC (9.8%,4/41;all P<0.01).Of 71 cases with ASCUS and ISIL without treated,none of HPV L1 positive cases(0/55)progressed in cytology,while 19%(3/16)of HPV L1 negative cases progressed to ASC-H,HSIL(P<0.01).Conclusion The expression rates of HPV L1 protein in liquid-based cell specimen is decreased as the cytopathology diagnosis severe degree.which may imply the histopathology diagnosis of cervix,predict the progression of cervical lesion,and help to treat the cases with ASCUS and LSIL.