The influence of different dosages of irradiation, temperatures of hot air, thicknesses of the slice carrot on the characters of dehydration and surface temperature for the irradiated carrot were studied. The results showed that three factors affected the characters of dehydration: irradiation dosage, temperature of hot air, and thickness of the slice carrot. With the increase of the dosage, both the rate of dehydration and the surface temperature for carrot increased. Then, the microstructure and water activity were also studied. The results showed that the membrane of the cell wall and vacuole of the irradiated samples were broken. The great dosage brought on the high water activity. These changes were the main cause for the characters of dehydration and surface temperature irradiated carrot. 