Objective To investigate the application of transvaginal color Doppler ultrasonography in the diagnosis of pregnancy at the incision of lower segment cesarean section. Methods The clinical data of 34 patients with pregnancy at the incision of lower segment cesarean section were collected. The imaging characteristics of transvaginal color Doppler ultrasonography was analysed. The abnormal echoes of the isthmus of anterior wall of the uterus were observed, and the relationship among its shape, size, incision and local blood flow was explored. Results The diagnosis of all the 34 patients were confirmed by transvaginal color Doppler ultrasonography. In 20 patients, the yolk sacs were detected at the incision of lower segment cesarean section of the anterior wall of the uterus, and hybrid echoes were observed on lower part of uterus in the other 14 patients. Conclusion Transvaginal color Doppler ultrasonography is a very effective method for diagnosis of pregnancy at the incision of lower segment cesarean section.