In order to satisfy the quality of service (QoS) of the application on Internet, Internet engineering task force (IETF) has presented a set of network service mode such as IntServ/RSVP (Integrated Service/Resource Reservation Protocol), DiffServ (differentiated service) and MPLS (multi protocol label switching). All of these service modes need a correlative QoS routing mechanism and algorithm to assign an adapted route. Based on the research of existing routing algorithms, a new pre-computed QoS routing algorithm CCPF(classified minimum cost path first)is put forward,which uses bandwidth as a basic metric and gives a weighted cost function as a path optimal criterion.By simulation,this algorithm is compared with the others.The results show that it can get differet routes among different bandwidth-ranges to support multipl service modes.