A wavelength buffersize method for effectively reducing wavelength routing optical network blocking rate belongs to the technical field of reducing construction blocking rate in the optical communication network. The method comprises: the proposed wavelength buffersize method adopting some route and wavelength distributing method to calculate route and set up connection on the ''non buffersize wavelength'', when the network instantaneous service strength is low; however, when the network instantaneous service strength is strengthening suddenly if the network resource of the ''non buffersize wavelength'' can not meet the construction requirement, the method selectively setting up connection for new service on the buffersize wavelength based on the parameters such as service precedence and network state so as to effectively improve the resource utilization factor in virtue of the time unbalanced distribution of the network resource and further reduce the high, medium precedence service or block rate of the whole network.