Owing to the fact that the current interconnected power system is incapable of fairly distributing area primary and secondary frequency regulation obligation， a more rational distribution mode of area frequency regulation obligation is presented. In order to guarantee frequency quality and a fair distribution of area frequency regulation obligation， the mode first rationally determines the total system frequency bias coefficient， and then fairly distributes each area's frequency bias coefficient. So it can arrange a more rational and desirable secondary frequency regulation characteristic for each area from top to bottom. Meanwhile， in order to improve the area primary frequency control ability， each area's primary frequency control ability is required to achieve the area's designated secondary frequency regulation obligation to enable it to realize fair distribution of area primary and secondary frequency regulation obligation. Hence the frequency bias coefficient is endued with a new function， that is， by rationally setting the area's frequency bias coefficient， not only will the frequency bias coefficient restrict the area secondary frequency regulation characteristics， but also it will become a baton for directing and improving the area primary frequency control ability to meet the requirements of the objective.