Abstract: The pharmacokinetics of nevin fibrinolytic enzyme (NFE) was studied by 125I-NFE as a tracer. Experiment results have showed that the time-concentration curve mainly was fitted to a two-compartment model after i.v , and its T1/2β were 6.1h(0.02u/kg),6.3h(0.04u/kg)and 5.6h(0.08u/kg) respectively. The 125I-NFE was found to be distributed w idely in organs of mice after iv , the peak concentration of 125I-NFE in organs appeared at 3h , and its values were as follows: 1.34%(kidney) , 1.09%(lung) , 0.90%(liver) , 0.90%(spleen) , 0.51%(heart) , 0.45%(muscle) and 0.29%(brain). The 85.6% of 125I-NFE was excreted in urine and only 5.4% in feces in 72h after iv. The percentage of gall excretion in rats was 12 in 8h after iv.