Abstract: This article described the loss of iridium-192 radioactive source in Nanjing and estimated the physical doses of exposed individuals. Point source formula was used to estimate the dose rates of the exposed individuals at distances from the point source. Absorbance doses and effective doses were estimated using relevant parameters and factors. Several people were exposed in the accident. The man, surnamed Wang, was exposed to iridium-192 with a thigh dose as high as 150 Gy, a hand dose up to 14 Gy, and a whole-body effective dose of 2.5 Sv; his biological dose estimate of chromosomal aberration was 1.3 Sv. The whole-body effective dose was about 270 mSv for his wife and less than 40 mSv for the other exposed individuals. Wang reported higher whole-body and partial-body radiation doses and diagnosed as acute and mild radiation-induced diseases according to the clinical manifestations and biological doses, while others have no obvious clinical symptoms.