Abstract: An experimental method of preparing carrier-free 203Pb radioactive tracer by cyclotron is presented.203Pb is produced by 203Tl(d,2n)203Pb re action by using T13O3 target and 15 MeV deuteron beam bombardment. Highly pure 203Pb tracer is finally obtained from irradiated target through a radiochemical separation procedure with Tl content about 1μg/m1. Chemical recovery is 71±5% ,and 203Pb yield at the end of bombardment is 180±36μCi/μA·h.Using this tracer,we have succeeded in determining lead content in biological samples by isotope dilution-substoichiometric analysis and toxicological investigation in rats.