A method for determining a routing path, includes: receiving a service connection request information which includes a source node identifier and a destination node identifier; based on a network topology information comprising a wavelength link and logical link and the service connection request information, looking for a path whose cost function value is minimal between the source node and destination node in each wavelength plane, where the cost function value of the said logical link is less than the cost function value of any wavelength link; determining the said path whose cost function value is minimal as the routing path of the current service. Also a routing path determination unit utilizes sufficiently the network bandwidth resource by preferably using the logical link and considering that the available bandwidth and the influence of the wavelength link number on the path choice in the existed logical link.