Objective To study the clinical application and complications of umbilical arterial catheterization(UAC)in premature infants.Methods From January 2021 to December 2022,premature infants with UAC successfully inserted in NICU of our hospital were enrolled.According to birth weight(BW),the infants were assigned into three groups:<1 000 g,1 000~1 499 g and ≥1 500 g.The perinatal data,UAC usage,UAC-related complications and risk factors of UAC-related complications were retrospectively analyzed.Results A total of 39 premature infants received UAC,with gestational age 29.3(27.3,30.4)weeks and BW 1 100(900,1 310)g.The insertion length(IL)of UAC was calculated using the average value of two formulas:a,IL(cm)=4x BW(kg)+7;and b,IL(cm)=3xBW(kg)+9.The accuracy of tube end position was determined using chest/abdomen radiography.30(76.9%)cases had accurate position,6(15.4%)had higher position and 3(7.7%)had lower position.The proportion of appropriately positioned tube end in<1 000 g,1 000~1 499 g and ≥1 500 g groups were 80.0%,76.5%and 71.4%,respectively,without statistically significant differences(P>0.05).No significant differences existed among the three groups in UAC duration and UAC routinely removal rate(P>0.05).9 cases(23.1%)of UAC were removed for specific reasons,including 4 cases of arterial spasm,2 cases of withdrawal of treatment,1 case of tube end displacement,1 case of abdominal distension and 1 case of death.21 cases received 1 U/ml heparin(0.9%NaCl solution)0.5~1 ml/h arterial infusion.23.8%(5/21)had hypernatremia and the level of sodium became normal after reducing the concentration of NaCl solution.Arterial vasospasm occurred in 4 patients with skin color changes of one side of the lower extremities.After UAC removal,the skin color returned to normal.Conclusions UAC is helpful and safe for preterm infants,however,its complications should be alerted to.