The invention relates to a method for determining routing path, which comprises the step of receiving service connection and request information, wherein the service connection and request information comprises a source node identification and a destination node identification; according to network topology information of a wavelength link and a logic link and the service connection and request information, a path of minimum cost function values is searched between source nodes and destination nodes on various wavelength planes; the cost function value of the logic link is smaller than that of any wavelength link in the network; and the path of the minimum cost function value is determined as the routing path of current service. The invention also discloses a determination unit of routing path. According to the invention, the logic link is preferably used, the influence of the available bandwidth and the wavelength link quality in the prior logic link on the path selection is considered, and bandwidth resources of the network are fully utilized.