唐代的身分制度，充分表現在唐律中；唐律的主賤關係，具有維護階級秩序的特色。唐律的家主有三個法定要件，即同籍、良口、合有財分。三者需同時成立，才算是家賤之主。大致上即以家長為核心至其期親所畫定之範圍。法律上的主賤關係可以及於主死之後，或放良、免賤之後。唐律直接觸及的主賤關係有十二種類型，包含刑事、民事與訴訟各領域。主賤相犯的刑度差距懸殊，正是不對等身分的反映，從其中可以看到唐政府用法律建構並維護等級秩序的用心。家主的概念因時代而異，唐律的家主或主賤關係在中國歷史上相當特殊，這與中古時期家庭擴大化，良賤制度化的背景有絕對關係。透過主賤關係，可以看到唐代身分階層的多樣性，與等級秩序的嚴整性。

The hierarchical system of Tang Dynasty was expressed explicitly and thoroughly in Tang Code; to put it differently, the master-servant relations disclosed in Tang Code served to maintain hierarchical order. Three legalizing conditions qualify a household master: identical household registration, non-servant status and legal right to property, lacking any of which shall make a household master ineligible. The system is centered with a household master, as remotely referring to a relative who shall take to mourning for a year at minimum. Legally defined master-servant relations can be expanded till the passing away of a master or till the servant who is liberated of servitude. Twelve types of master-servant relations were announced in Tang Code, compassing criminal prosecution, civil prosecution and proceedings. Extent of punishments vary tremendously, reflecting an unequal status of master and servant, and demonstrate the mind and intention of the ruling class of Tang Dynasty—constructing and maintaining the stratification order. The concept of household master varies from the change of age, while the household master and master-servant relations play a spectacular part in the history of China, immensely influenced by the expanded household and the construction of master-servant system in the middle ages. Viewing from master-servant relations, one may perceive the diversification of social class of Tang Dynasty and the rigorous strictness of stratification order.