Abstract: ~(125)I-AaT, prepared by oxidant-chloroamine T from the related venom of Agkistrodon Acutus, is given to a rabbit by intravenous injection, and then, the distribution of the toxin in the rabbit and its Pharmacokinetic characters have been studied. The rabbit is killed five hours after the injection, and tthe radioactivity in each tissue calculated. The result indicates that the blood-brain barrier exist in the body, and large quantity of by-Products of ~(125)I-AaT metabolism is eliminated from urine by the kidney. For Pharmacokinetics, the computer simulated curve demonstrates that the result conforms to the Two Compartment Model. The fast component half-life T_(1/2α) is 3.15mins., slow component T_(1/2β) 165 mins., and the biological half-life T_(1/2) is 75.2 mins. V_(?), V_t and V_c have been analyzed, and we think Preliminarily that there must have been a corresponding receptor to the toxin in the body.