To investigate the value of transvaginal three-dimensional (3D) power Doppler ultrasound in the diagnosis of benign and malignant endometrial diseases.A total of 144 patients with endometrial thickness ≥4 mm were enrolled. Endometrial thickness was measured by transvaginal 3D B-mode ultrasound, while blood signals were detected by 3D power Doppler ultrasound. Endometrial volume (EV), vascularization index (VI), blood flow index (FI), and vascularization flow index (VFI) were calculated. All histopathological diagnoses of endometrium were obtained.There were 86 benign and 58 malignant cases. There were statistically significant differences between two groups in endometrial thickness [1.50 (1.30, 1.80) vs 2.30 (1.80, 3.20), P < .001], EV [10.62 (7.14, 17.36) vs 28.94 (9.59, 67.96), P < .001], VI [6.07 (3.61, 10.33) vs 12.01 (7.50, 19.87), P = .001], FI [27.42 (24.45, 31.33) vs 32.98 (30.22, 35.40), P < .001], and VFI [1.58 (0.92, 3.32) vs 4.28 (2.24, 6.41), P < 0.001]. Sensitivity and specificity of endometrial thickness were relatively high [endometrial thickness (86.2%, 76.1%), EV (48.3%, 97.7%), VI (72.4%, 69.8%), FI (72.4%, 74.4%), and VFI (72.4%, 74.4%)]. There was no significant difference in any parameters of the endometrium between different stages (Ia, Ib, II, and above) or phases (G1, G2, and G3) of Ia phase of endometrial cancer (all P > .05).Transvaginal 3D power Doppler ultrasound is valuable in the differentiating benign and malignant endometrial lesions.