Abstract: Objective：To determine whether grade 3 endometrioid endometrial carcinoma (G3EEC) could be more akin to type Ⅰ or Ⅱ cancer. Methods：Between January 2000 and December 2010，4 811 patients were extracted from the collaboration hospitals in the center for endometrial cancer control and presentation in Guangdong, China. We performed a retrospective study of clinicopathological parameters and survival data in three different populations including grade 1 and grade 2 endometrioid endometrial carcinoma (G1EEC/G2EEC, n=4 026), G3EEC (n=619), uterine serous carcinoma and clear cell carcinoma（USC/CC, n=166). Results: In G3EEC group and USC+CCC group, propotion of obese and fatty women（40.6% vs. 37.7%, P=0.625）, propotion of nulparity(4.2% vs. 2.5%, P=0.323), percentage of menopause（６4.1% vs. 70.5%，P=0.127）, percentage of abodominal symptoms(4.7% vs. 6.0%, P=0.481), percentage of advanced surgical stage（３２.8% vs. 31.3%, P=0.7２） were assemblｅd，and there was a significant difference while compared to G1EEC/G2EEC. G3EECs shared similar pathological features including percentage of lower uterine segment involvement（１4.1% vs. 18.1%，P=0.279）, deep myometrial invasion （43.6% vs. 39.8%，P=0.372), invasion of lymph-vascular spaces(9.4% vs. 11.4%，P=0.425), incidence rates of cervical stromal invasion(23.6% vs. 21.7%，P=0.607) and lymph node metastasis incidence(24.7% vs. 24.3%，P=0.927), higher than G1EEC/G2EECs . There was no significant difference in overall survival(P=0.544) and progress free survival(P=0.939) for G3EECs and USCs/CCCs. Using a Cox regression analysis, G3EECs had a significantly decreased overall survival and progress free survival compared to G1EEC/G2EECs [HR=4.147，95%CI(2.573-6.683)，P＜0.001；HR=3.365，95%CI(2.300-4.923)，P＜0.001]. Conclusions：According to clinicopathologic features and outcome, G3EEC may be better characterized as type Ⅱendometrial cancer.