Objective To design an auxiliary device for lateral position management of neonatal peripheral venous indwelling needle puncture and examine its effect on occurrence of complications in NICU infants. Methods One hundred and thirty ⁃two newborns were randomly assigned as the study group and another 132 newborns as the control group，the two groups compared in regard to premature and term newborns. In the study group，the self⁃designed device was used to adjust the position of the limb on the side of the puncture immediately after the venous indwelling needle puncture，and in the control group no position adjustment was done. The duration of venous catheter indwelling，the complications and related adverse events were compared. Results There were significant differences in oozing at the puncture point，phlebitis，dressing loose，poor infusion and catheter indwelling duration between the term newborns of the two groups（P < 0.05），while between the premature neonates of the two groups，there were significant differences in oozing at the puncture point，phlebitis，poor infusion due to joint flexion，and catheter indwelling duration（P < 0.05）. There was no significant difference in dressing loosening between the two groups（P > 0.05）. No adverse events except phlebitis occurred in both groups. Conclusion The device with joint extension belt designed for assisting the postural management of neonates after intravenous cathe⁃ terization is good for the posture adjustment as well as for the fixation and adjustment of the joints，which provides multiple safety guarantees for the neonates.