Objective: To evaluate the risk of lymph node metastasis and figure out necessity of lymphadenectomy in grade 3 endometroid endometrial cancer (EEC) patients. Methods: From 2009 to 2019, 3751 endometrial cancer (EC) patients were diagnosed at Gynecology Hospital of Fudan University, 1235 EEC patients were enrolled in multivariable analysis. 381 patients had survival analysis attributed to sufficient follow-up information. Kaplan-Meier curve and logrank test were used to analyze the survival rate. Results: Among 1235 EEC patients, multivariate analysis showed lymph-vascular invasion (LVSI), adnexal involvement (AI), cervical stroma involvement (CSI) were independent risk factors of lymph node metastasis (LNM) in grade 3 (G3) cohort (OR=3.45, 5.83, 8.93; 95% CI 1.12-10.64, 1.52-22.35, 2.85-28.00 respectively). LNM rates increased from 3.3% to 75% for EEC G3 cohort with the increase of risk factors from one to three. There were no differences between G3 and grade 1&2 (G1&2) in overall survival or progression free survival. Similarly, no survival advantage was found for EEC G3 patients at early stage with different plans of adjuvant treatment. Conclusion: When EEC G3 patients combine with one or more risk factors including LVSI, AI and CSI, lymphadenectomy is recommended. For those with only one factor of G3, it is recommended to evaluate the status of lymph nodes by considering other methods such as sentinel lymph node biopsy technology to avoid overtreatment. Survival analysis showed no difference in EEC G3 cohort compared with G1&2. Also, different plans of adjuvant treatment had no impact on overall survival for EEC G3 patients.