Abstract: carbomethoxy-3β-(4'-iodophenyl)nortropane(nor-β-CIT) and it's labelling precursor 2β-carbomethoxy-3β-(4'-tribuylstannylphenyl)nortropane are synthesized, the chemical structures of nor-β-CIT and it's intermediates are confirmed by IR, MS, HNMR and rotation. The Radiochemical purity of 131 I-nor-β-CIT is over 95% evaluated by HPLC and TLC. Biodistribution in rats indicate rapid uptake and slow clearance of 131 I-nor-β-CIT in brain (2.30, 2.54 and 1.22 %ID respectively at 5, 30 and 240 min after injection). It displays high radiouptake in thalamencephalon, midbrain, hippocampi and frontal lobe, the maximum values are 1.77, 1.78, 1.54 and 2.13 %ID respectively at about 1 hour after injection. The value of uptake in frontal lobe is greater than in temporal lobe and in parietal lobe(2.13, 1.92 and 1.87 %ID), which are consistent with the distribution of serotonin transporter in the brain.