Abstract: Objective To evaluate the clinical value of the video colposcopy in screening cervical intraepithelial neoplasia（CIN） in cytological negative and smooth cervices by optically gynecological examination. Methods A total of 1050 women， whose cervices showed smooth by optical examination and cytological negative， were examined with electronic colposcopy in gynecological clinic， and biopsy was taken when the double abnormality of acetowhite epithelium and iodine negative， and other abnormal images were shown. A restrospective analysis of these cases was performed. Results （1） Four hundred and fiftyeight of 1050 cases were examined by biopsy, including 56 cases of abnormal tissue with cervical polyp or polypoid tumors. Among them， 68 cases of CIN were found， including 11 cases of CINⅡ／CINⅢ.（2） Seventytwo of 1050 cases showed the doubleabnormality of acetowhite epithelium and iodine negative. Among them， 64 cases were CIN determined by biopsy. And the positive predictive value of the doubleabnormality of acetowhite epithelium and iodine negative under colposcopy was 88.9％， with a false negative rate of 3.3％.（3） Among 458 women who were examied by biopsy， only one of 350 samples from cervical polyp tissue was CIN（0.3％）， while 67 of 164 samples from the tissues with abnormal colposcopic images were found to be CIN（40.9％）， indicating the close relation between abnormal colposcopic findings and CIN.（4） The results of agedistribution analysis showed that， in the 164 cases with abnormal featares under colposcopy， the incidence of double abnormality of acetowhite epithelium and iodine negative was higher in the age of sexual activity， just the same as the age distribution feature of CIN； while single abnormality of iodine negative appeared more in the age of over 50 years. Conclusion Abnormal features displayed by colposcopy， especially the double abnormality of acetowhite epithelium and iodine negative， has an important significance for the screening of cervical precancerous lesions such as CIN. For this purpose， colposcopic examination is necessary even for the cases of cytological negative and smooth cervices.