Two contradictory requirements of the on-board switch scheme are the Quality of Service (QoS) performance and the complexity limitation. Therefore, in order to achieve a better trade-off between the performance and the resource utilization, a new onboard switch scheme based on Differentiated Service (DiffServ) is proposed. Under the scheme, a QoS mapping module adopting the concept of the (m,k) model, which implements mapping between the terrestrial and satellite network traffic, is added to the terrestrial satellite terminal (ST). Additionally, according to the mapping results the on-board switch applying a double-Leak Bucket (LB) model controls the on-board traffic efficiently. In the end, Comparisons are made between the proposed scheme and the conventional one by simulation.