Abstract: Basing on the DOS models aggregating ability, the client layers services with different QoS requirements can be mapped directly into the optical channel. Then the different QoS requirements of the client layers services can be reflected by the different priorities of the connection request at the border optical node in a DOS domain. A wavelength graph method is presented in the multi-fiber WDM optical transport network to reduce the blocking probability of the connection request. Two optical QoS routing strategies, concentrating method and equalizing method, are proposed. The two methods are compared by simulation results of the network performance in different dynamic traffic load situations.