Objective To explore the optimal concentration of heparin sodium solution, which to seal up intravenous indwelling needle, in patients with Ⅳ thrombocytopenia. Methods A total of 90 patients withⅣthrombocytopenia who required intravenous indwelling needle were randomly divided into three groups which namely A, B and C groups with 30 cases each. A group was sealed up the tube of intravenous indwelling needle with 1 ml heparin sodium solution of 6.25 U/ml, B group with 12.50 U/ml and C group with 25.00 U/ml. The change of the platelet count, plasma prothrombin time (PT), activated partial thromboplastin time (APTT), plasma fibrinogen (Fbg) after extubation were observed in three groups and the incidence of blocking up and retention time were compared among three groups. Results The change of the platelet count, PT, APTT, Fbg were showed no statistical significance among three groups (P>0.05). The incidence of blocking up was 66.7%(22/30) in A group , 43.3%(13/30) in B group and 16.7%(5/30) in C group. They were showed statistical significance (χ2=15.000, P < 0.01). Retention time of tube above or equal to 3 days were observed respectively 13 person (43.3%,13/30) in A group, 21 cases(70.0%, 21/30) in B group, 25 patients(83.3%, 25/30) in C group. All above were showed statistical significance (χ2=11.000, P<0.01). Conclusions Heparin sodium 25.00 U/ml sealing up the tube of intravenous indwelling needle is safe in patient with Ⅳthrombocytopenia, which will reduce the ration of blocking tube and extend the life of tube.