Objective To compare the preventive effect of normal saline and heparin on central venous catheter-relatedthrombosis in rats. Methods Forty Sprague-Dawley rats were randomized into a normal saline (NS) group and a heparin group, with 20 in each. Central venous catheter was placed into rat model to simulate clinical infusion. The catheters were locked daily with NS or heparin after use. The specimens of rat models were taken on the 1st, 4th, 7th, 10th and 14th day to observe the development of thrombosis. Results During catheter dwelling, both groups had 1 case with catheter out of the vein. The NS group did not develop catheter blockage, but 2 cases in heparin group had catheter blockage.The thrombosis rate was 73.68% in the NS group and 78.95% in the heparin group.There were no significant differences in incidence rate of blockage and thrombosis between the two groups（P＞0.05 for both）.In the early stage of catheter-related thrombosis, the severity in the heparin group was milder than the NS group, but in the late stage, it was milder in the NS group than the heparin group. Conclusion NS is effective as heparin on prevention of catheter-related thrombosis, however, from comprehensive evaluation, NS is superior to heparin.