Background: To evaluate the preoperative diagnostic efficacy of 3D-MRI for the depth of myometrial invasion of endometrial carcinoma. Methods: A total of 116 patients with endometrial carcinoma who had undergone pelvic MRI before surgery were included. Mimics 21.0 (Materialize Co., Belgium) software was used to reconstruct three-dimensional MRI models (3D-MRI). The tumor volume and surface area, uterine volume and surface area were measured, and the tumor volume ratio was calculated. TVR (Tumor Volume Ratio) = tumor volume/uterine volume, TAR (Tumor Area Ratio) = tumor surface area/uterine surface area. Postoperative pathology was used as the gold standard to compare the accuracy, sensitivity, specificity, negative predictive value, and positive predictive value of conventional MRI and 3D-MRI in preoperative assessment of endometrial carcinoma myometrial invasion. Results: The accuracy and specificity of 3D-MRI in the diagnosis of deep myometrial invasion were better than conventional MRI (p 0.05). There was no statistically significant difference in tumor volume or surface area between stage IA and stage IB (p > 0.05), while TVR and TAR showed significant statistical differences (8.05 \pm 0.66 vs. 19.12 \pm 3.20, p 0.01; 21.38 \pm 1.04 vs. 35.15 \pm 3.42, p 0.01). Further analysis, the area under the ROC curve of TVR is 0.738, p 0.01, and the best cut-off value is 13.59%; the area under the ROC curve of TAR is 0.770, p 0.01, and the best cut-off value is 27.41%. Conclusions: Preoperative 3D-MRI can effectively assess the myometrial invasion of endometrial carcinoma.