Abstract: Objective :To investigate the expression of the proliferation marker Ki67 in endometrial diseases and its clinical significance for the incidence of endometrial carcinoma and evaluation ofprognosis. Methods :Experimental group: 150 cases including 30 of endometrial hyperlpasia, 30 ofatypical proliferation and 90 of endometrial carcinoma; control group: 30 cases including 15 of prolifer-ative endometrium and 15 of secretory endometrium. The expression of Ki67 in these cases with im-munohistochemistry technology was detected. Results :There was almost no Ki67 expression in secreto-ry endometrium and the expression was mild in proliferative endometrium. In endometrial hyperplasiaand atypical proliferation, Ki67 expression can be observed but there was no statistically significancebetween the two groups (P>0.05). Compared with control groups respectively, there was no significancetoo (P>0.05). In endometrial carcinoma, the expression increased obviously,which is higher than benigndiseases and control group prominently (P<0.01). The positive rate of Ki67 antigen increased with theincreasing of clinical phase and grade of cellular differentiation. Conclusions :Ki67 antigen is related to the incidence of endometrial carcinoma. The over expression of Ki67 indicates a poor prognosis of pabents with endometrial carcinoma.