In the present study, I aim to clarify social structure and differences of social interaction among different aged giraffe’s (Giraffa Camelopardelis) in Katavi National Park, Tanzania. I recorded giraffe’s sex, herd size and individual identify by pattern of marking on their necks. I estimated age on the basis of body size. The study about social structure was conducted around HQ and IKUU. As a result, I observed more calves around HQ than IKUU. A previous study revealed that predation pressure around IKUU is higher than HQ, which may produce the difference of the number of calf. Mother giraffe that had a calf tended to form a herd with other mothers that had calves. This was probably because the mother giraffes may form a herd to keep their offspring from predation. Perhaps they may share responsibilities with other mothers. I also conducted focal animal sampling of calves and juveniles, I recorded social interaction and distance between focal animal and other individuals. The result shows mean distance between calves was shorter than that between calves and mothers. The calves tended to make longer distance with adult males than that with females, while juvenile giraffes tended to be closer not only to peers but also to adult males or females. This is probably because of developmental behavioral change, which means that calve tend to spend most of the time for resting or playing, but not spend same time to feed like adult. In addition they tend to gather each other for resting to beware predator, which might made calves have preference to physically close to other calves. Juveniles move in larger area than calves and spend more time to feed and ruminate. Therefore juveniles have more chances to encounter other giraffes than calves. While they feed and ruminate, they tend to come closer to other adult ones to avoid predator. The bush may make the juveniles and calves difficult to detect predator. This may be because social relationships change as result of changes of home range and developmental behavioral pattern.