北魏自文成帝以來雖有將罪犯集體徙逐邊地的措施，但究其性質，仍是皇帝矜死赦宥的恩德，屬於死刑的代刑而非刑律中的正刑。直到孝文帝太和十六年以前，北魏的刑罰體系，主要是以門房之誅、死刑、刑罪三者構成，並無流刑的位置。太和十五年議定新律，遂將流徙之事法定化。太和十六年頒定的新律中，流刑才正式成為法定的正刑。北魏流刑既在恕死徙邊、充實鎮戍這樣基礎之上發展而來，那麼，流徙邊地和配充兵戶兩項要件，似乎沒有消失。流刑犯既是一律流徙沿邊軍鎮，配充兵戶，那麼流刑自然就沒有道里之差的必要。另外，太和制訂流刑時，可能規定流人舉家強制隨行。流人配充兵戶無非是為了保障兵源，所以除非皇帝恩詔寬免，否則流人是終身流放，返鄉無期的。 北齊流刑承襲《魏律》而來，屬於刑律的正刑，但服流刑者的條件是「論犯可死，原情可降」，也帶有死刑替代刑的性質。犯人既是投於邊地為兵卒，自然也是如同北魏一樣，流刑不必也不可能有明白和標準的道里之差了。既是降死從流，故處罰仍重，犯者須鞭、笞、髡，然後流於邊地為兵卒，終身不得返鄉。北周流刑自二千五百里至四千五百里，共分五等，即有所謂「道里之差」。除了道里之差外，流刑犯強制苦役六年，俟六年苦役期滿，犯人可以放免返鄉。道里之差、苦役年期、流放年限等，皆北周迥異於魏齊之制。此外，罪犯流放以前尚有附加刑的鞭與笞，此點與魏齊之制相仿。 北周流刑道里之差、強制苦役、附加刑、流放年限等要素，都為隋代所承襲。但隋制輕於周制：就里程言，隋是從一千里到二千里共三等；就居作年限言，隋是從二年至三年不等；就鞭笞之數言，隋最高是杖一百六十；就流刑年期言，隋代縮短為五年放免。簡而言之，北周流刑的四項要素明顯皆為隋代所繼承，這點是討論隋律淵源者所經常忽略的。唐代的流刑與魏齊周隋的關係是如何？唐代流刑「道里之差」和強制勞役，明顯是承襲周隋舊制。至於妻妾強制隨流和流人終身遠逐，應是參照魏齊之制而來。唐代流刑的骨架源自周隋，但亦吸收了部分魏齊的因子。概而言之，流刑的發展脈絡是： 流刑最後是在北朝而不是南朝發展成立，究其原因，筆者以為這既牽涉到南北政權採用了不同的方式，來解決肉刑廢除後造成的刑罰漏洞，也牽涉到北朝獨特的世兵制。前者是必要條件，後者為充分條件，二者適時配合，終使流刑正式誕生。然而，當恕死徙邊措施法制化之後，罪犯徙邊充兵成為常態，軍隊地位的低落，遂一發不可收拾，最終導致「六鎮之亂」的爆發。

There was penalty to exile criminals collectively to frontier in Northern Wei Dynasty since Emperor Wen Cheng(452-465), but if we study it thoroughly, the banishment was not a formal punishment. It was the mercy of the emperor to replace the death penalty. Before Tai He 16th year(492) of Emperor Xiao Wen(471-499), the penalty system of Northern Wei Dynasty consisted of three parts –Capital Punishment to whole clan; capital punishment & penal servitude. There was no place for banishment. After a discussion on their new penalty system in Tai He 15th year and finally in next year, banishment became a formal punishment. The development of banishment in Northern Wei Dynasty was based on two elements : it was a replacement to the death penalty & the criminals were exiled to frontier as soldiers to safeguard the country. So, there was no grade of this punishment. Moreover, when the punishment established in Tai He period, the family members of the criminals were forced to go together with them. As this punishment was also served to ensure there were sufficient soldiers, the criminals were exiled to the frontier for life. They could not return to their own province unless there was a pardon from the emperor. The banishment of Nothern Qi Dynasty(550-577) was originally inherited from the Northern Wei Dynasty, and it was a formal punishment. It also served as a substitute to the death penalty, but the criminals had to be flogged, beaten by light rod and their heads shaved, and then exile to frontier for life. There was no grade of exile in the Northern Wei Dynasty but there were 5 grades in Northern Zhou Dynasty(557-581), ranged from 2,500 to 4,500 miles, that means there were difference in mileages. Besides mileages, the criminals had to perform hard labour for 6 years, and after that, they might return to their native provinces. Difference in mileages, periods as hard labour and years of exile in banishment carried out in Northern Zhou Dynasty were quite different from those in Northern Wei & Qi Dynasties. However, the criminals had to be flogged & beaten before exile were similar to those in Northern Wei & Qi. The difference in mileages, periods as hard labour and years of exile in banishment in Northern Zhou Dynasty were inherited by Sui Dynasty. But the latter took a step forward: 1) Mileage – Sui from 1,000 to 2,000 with 3 grades; 2) Periods as hard labour – Sui ranged from 2 to 3 years; 3) Number of flog and beat received – Sui with maximum 160. 4) Year of exile – Sui with maximum of 5 years. Simply speaking, the above 4 elements were all taken from Northern Zhou Dynasty. What was the relationship between the banishment in Tang and Wei, Qi, Zhou & Sui Dynasties? There were ‘Mileage difference’ & ‘forced hard labour’ in Tang’s banishment, and this indicated that the principle of this punishment was adopted from Zhou & Sui Dynasties. Whereas families were forced to exile with the criminals and all of them were sent for life long were adopted from Wei & Qi Dynasties. Therefore we can state that banishment in Tang Dynasty was adopted from Zhou & Sui, but also learnt some from Wei & Qi. Below is the development history of banishment: Nothern Wei Dynasty Northern Zhou Sui TangBanishment was finally developed completely in Northern but not in Southern Dynasty. This was due to the different solution adopted by the 2 dynasties to deal with the loophole existed when the corporal punishment was abolished, together with the unique military system applied in Northern Dynasty. The former is the essential condition, and the latter is the sufficient condition. When the 2 factors merged, the formal banishment was established finally. However, when these criminals became soldiers, this hampered the status of army and finally erupted ‘The Rebellion of the Six Military Posts’.