Network availability is one of the important indexes of the Service Level Agreement（SLA）in the field of telecommunications and its improvement is a realistic issue for Internet Service Providers（ISP）and also a hot topic of research in the academic circles at home and abroad.On the basis of the existing researches on Wavelength Division Multiplexing（WDM）networks

this paper develops an heuristic algorithm using Java language and presents an M∶Nprotecting technology-based availability analysis model.The results show that this technology can enhance the network availability to a great extent and the link protecting technology can achieve still higher availability at the expense of consuming the reserved network resource than the path protecting technology.