This research paper aims at investigating the culture of Paiwan traditional social structure regarding to the literature review and depth interview with the superiors of Paiwan tribes. Results of the study show that the basis of the traditional aristocratic system in Paiwan tribes originated from firstborn child as inheritor of family. This system influences the development of all relatives. That is, the other younger brothers and sisters not only give their respect to the original family but also offer all necessary helps to honor their original family. The firstborn inheritor also has the duty to host the life rite for the relatives and gives them necessary supports in emergency situations.