本文點出《資治通鑑》、《新唐書．柳沖傳》、《魏書．官氏志》中出現的「四姓」一詞，並爬梳過往學者對中古「四姓」的討論，可初步統整為三個說法，並提出「四姓」意涵在北魏到唐代間的轉變，有其政治與社會意義存在。

There are two main points in the article. The one is to find out that “four surnames” present in " Zi Zhi Tong Jian ", "Xin Tang Shu", "Wei Shu”, and then to review the discussions about “four surnames”, which can be initially divided into three view, in medieval China by scholars. The other one is to propose that there existed political and the social implications in the meaning of “four surnames” changed between Northern Wei Dynasty's and Tang Dynasty.