Abstract： Objective To explore the relation between sealed tube method and retention time of intravenous catheter system . Methods Adopt direct injection seal-tube method, saline injection seal-tube method and heparin liquid seal-tube method with common intravenous catheter were adopted the intravenous catheter's retention time and incidence of phlebitis were observed. Results The retention time in direct injection seal-tube group and saline injec-tion seal-tube group respectively prolonged of 25.7% and 19. 3% compared with heparin liquid seal-tube group.There was significant difference (P < 0. 01 or P < 0. 05) through statistical analysis. But there was no significant differ-ence(P 0. 05) between direct injection seal-tube group and saline injection seal-tube group in retention time. Theincidence of phlebitis in both direct injection seal-tubo group and saline injection seal-tube group were below to the heparin liquid seal-tube group. There was significant difference(P 0. 05) in the three groups. But there was no sig-nificant difference(P 0. 05) between direct injection seal-tube group and saline injection seal-tube group in the inci-dence of phlebitis. Conclusion Direct injection seal-tube method and saline injection seal-tube method can signifi-cantly extend intravenous catheter's retention time and reduce the incidence of phlebitis.