Abstract: To estimate the radiation absorbed doses in humans due to intravenous administration of 618FLDOPA(18FDOPA) based on rats biodistribution data and appraise the security of 18FDOPA in humans. At 5, 30, 60, 90, 120 and 150 min after 18FDOPA is injected into rats through a tail vein, the rats are killed by cervical fracture and biodistributions in rats are determined. Radiation dosimetry in humans are calculated on the base of activity distribution in rats and the standard MIRD method using radioactivitytime curves for humans. The kidney is the organ receiving highest dose of 22.9 pGy/Bq, the brain receives a dose of 11.8 pGy/Bq, and other organs receive doses between 9 and 18 pGy/Bq. The effective dose is estimated to be 20.5 pSv/Bq. The results demonstrate that human radiation dosimetry can be estimated by the rats biodistribution data and provide an important data for clinical safe trial of 18FDOPA.