The forced labor system in the prior period of Northern Song Dynasty came from late Tang dynasty and Five dynasties.It exhibits some new characteristics including the alternates of main service kind from corvee to vocational service

the change of service object from age to property

the variation of service range from central to local government.The appearance of these characteristics not only took decentralization of central and local government as background

but also was associated with the change of finance and tax in that era.The change of forced labor system in that era was beneficial to lighten civil burden and realize fairness of corvee.It also oriented the development of the force labor system in ancient China.