Objective To explore the application effect of ultrasound guidance and X-ray positioning catheter tip in umbilical vein catheterization (UVC) in premature infants.Methods The clinical data of 42 premature infants with UVC indications admitted to Pingxiang City People's Hospital from June 2019 to December 2021 were retrospectively analyzed.According to different examination methods of catheter placement,they were divided into the X-ray group (n=20) and the ultrasound group group(n=22).The X-ray group adopted the method of adjusting the catheter tip by X-ray positioning after UVC,and the ultrasound group adopted the method of real-time ultrasound positioning to guide UVC.The catheter placement effects (one-time puncture success rate,catheter placement operation time,and catheter placement time),the degree of post-traumatic inflammation([C-reactive protein,CRP],[procalcitonin,PCT],[platelet,PLT]),the total incidence of complications (catheter obstruction,catheter displacement,local bleeding,exudation,infection,arrhythmia) were compared between the two groups.Results The one-time puncture success rate in the ultrasound group was higher than that in the X-ray group,and the difference was statistically significant (P＜0.05).The catheter placement operation time in the ultrasound group was shorter than that in the X-ray group,the catheter placement time in the ultrasound group was longer than that in the X-ray group,with statistical significance (P ＜0.05).Before catheterization,there were no significant differences in the levels of serum CRP,PCT and PLT between the two groups (P＞0.05).After catheterization,the levels of serum CRP and PCT in the ultrasound group were lower than those in the X-ray group,while PLT level in the ultrasound group was higher than those in the X-ray group,the differences were statistically significant (P＜0.05).The total incidence of complications in the ultrasound group was lower than that in the X-ray group,and the difference was statistically significant (P ＜0.05).Conclusion Compared with X-ray catheter tip positioning,ultrasound guidance in UVC can effectively improve the one-time puncture success rate,shorten the operation time of catheterization,prolong the indwelling time of catheterization,and reduce the degree of post-traumatic inflammatory reaction and the risk of complications.