Objective: To study the value of colposcopy in diagnosis of cervial diseases.Methods: 2989 women were examined with optical colposcope at Taian Central Hospital from July 2005 to Oct 2007,of which 766 were given biopsy under colposcope for pathologica analysis.Results: cervical intraepithelial neoplasia(CIN) were diagnosed in the pathology in 362,including 275 CINⅠ,55 CINⅡ,32 CIN III and15 Cervical Cancer,biopsy CIN rate up to 47.25%.86.74% of the patients with CIN were 20~39 years old,93.33% of cervical cancer were the patients aging 30~49,which is a very dangerous age of cervical cancer.30.17% of the total CIN subjects were with low-grade cercix uterierosion,among which CINⅡand CIN III were 29.09% and 31.25% respectively.And 10.49% of the total CIN subjects were with smooth cervices.Conclusion: Colposcope can be used to find CIN at early stage,and provides a key approach to diagnose early cervical cancers and CIN.