Objective:To investigate the clinical utility of intracavitary electrocardiogram (IC-ECG) localization technique in locating the tip of umbilical venous catheterization (UVC).Methods:From April 2020 to March 2021, premature infants admitted to the Department of Neonatology of the Third Affiliated Hospital of Guangzhou Medical University and received UVC were collected for a prospective study. According to whether IC-ECG was used to determine the position of umbilical vein catheter tip during catheterization, they were divided into IC-ECG group and control group. The differences of catheterization success rate, total incidence of catheter-related complications were compared between the two groups. The relationship between characteristic P waves and the position of the catheter tip in the IC-ECG group was also analyzed.Results:A total of 104 premature infants were enrolled, including 52 cases in IC-ECG group and 52 cases in control group. The catheter placement accuracy rate of the IC-ECG group was higher than that of the control group (53.8% vs. 28.8%, P<0.05). There was no statistically significant difference of the total incidence of catheter-related complications between the two groups ( P>0.05). Among the 40 cases with characteristic P wave changes in the IC-ECG group, 21 cases had normal P wave, of which 13 cases (61.9%) were with the correct position. And 19 cases had low-amplitude bimodal P waves, of which 15 cases (78.9%) were with the correct position. There was no statistically significant difference of the exact position rate of the catheter tips between the two types of P waves ( P>0.05). Conclusions:The use of IC-ECG localization technique in the process of catheterization of umbilical vein can increase the exact position rate of catheterization. Furthermore, when IC-ECG monitoring shows characteristic P wave changes to normal P wave or low-amplitude bimodal P wave, the tip of the UVC catheter may be located accurately.