Based on the theory of probability, a blocking probability model is proposed to investigate the blocking performance of the individual node in wavelength division multiplexing (WDM) wavelength routed all-optical networks. The blocking performance is relevant to the number of wavelengths multiplexed in each fiber link and the number of access fiber link ports, with (full or limited) wavelength conversion. The numerical results show that the wavelength routing node equipped with the higher conversion degree of wavelength converters has the better performance than the node equipped with lower ones. To enhance service efficiency of wavelength resource and to make the all-optical networks more flexible, virtual wavelength routing, wavelength converters in all-optical networks are needed. Trade-off between the performance and the cost is found in this paper. Then to guarantee blocking performance is precondition, wavelength routing nodes deployed with the low conversion degree of the wavelength converters are able to reach the definite blocking performance. The realistic and cost-effective way to construct nodes system in WDM routing networks is to use wavelength converters with weak capability.