Objective To investigate the significance of DNA ploidy analysis in diagnosis of atypical squamous cell of undetermined significance ( ASCUS).Methods From Jan.2009 to Jul.2011,875 women with ASCUS confirmed by liquid based thin layer cytology technique underwent DNA ploid analysis in Hubei Maternal and Child Health Hospital.Among 294 women underwent high risk HPV detection.All subjective were examined colposcopy directed biopsy at day 3 to 10 after menstruation.Results Among 875 ASCUS cases,553 cases with histologically as chronic cervicitis (63.2％),165 cases with cervical intraepithelial neoplasia (CIN) Ⅰ (18.9％ ),45 cases with CIN Ⅱ (5.1％),79 cases with CIN Ⅲ (9.0％) and 33 cases with cervical invasive cancer (3.8％) were confirmed by colposcopy.Totally 532 cases were observed with DNA heteroploid,and 343 were not observed with DNA heteroploid.When DNA heteroploid negative and more than or equal to three ploid were used to predict CIN Ⅱ or more severe cervical diseases,the sensitivity,specificity,positive predictive values and negative predictive values were 98.7％ and 90.3％,47.5％ and 46.1％,29.1％ and 40.8％,99.4％ and 92.1％,respectively.The amount of heteroploid cells ＞2.5c and ＞ 5c among every 100 detected cells in chronic cervicitis and CIN Ⅰ,CIN Ⅱ,CIN Ⅲ and cervix cancer were respectively 2.53 ± 1.99 and 0.10 ±0.07,2.24 ± 1.69 and 0.20 ±0.11,4.10 ± 1.91 and 0.28 ±0.19,7.97 ±7.33 and 1.27 ± 1.23,8.99 ±7.33 and 0.36 ±0.33,there was no statistical difference in amount of heteropolid cells between ＞ 2.5c and ＞ 5c at group of chronic cervicitis and CIN Ⅰ,CIN Ⅲ and cervix cancer (P ＞ 0.05).However,the amount of heteroploid cells at ＞2.5c and＞ 5c at group of chronic cervicitis,CINⅠ,CIN Ⅲ and cervical were higher than that of CIN Ⅱ significantly (P ＜0.05).Among 294 cases with high risk (HR) HPV detection,216 cases were HR-HPV positive,and 78 cases were HR-HPV negative.The pathology result by colposcopy at group of negative heteroploid,heteroploid ＜ 3,or ≥ 3 showed statistical distribution (x2 =115.2775,P ＜ 0.01).ConclusionDNA ploidy analysis can be used for ASCUS diagnosis,which can avoid excessive biopsy under colposcopy,in the mean time,CIN and cervical cancer could decrease missed diagnosis.