Abstract: The weight of main organ and their coefficient of 62 beagle dogs were measured.The results showed that in young age group,the weights of heart,lung and kidney were higher in male than in female. Both male and female, the weights of lung, thymus and thyroid in middle age group were higher than those of young age. The coefficient of the lung, thymus and thyroid were significant difference between the young and the middle age group，especially the difference of thymus coefficient was very significant.

Key words: Beagle dogs, Organ weight, Organ coefficient