The protection design for dynamic multicast traffic in wavelength division multiplexing(WDM) networks is studied.We propose a shared protection algorithm called SPR,which computes a minimum cost light-tree for each multicast connection request,and find a link-disjoint backup segment for each working segment on the light-tree.If a fiber link fails,SPR can reprovision new capacity for the vulnerable segments.The simulations show that SPR can efficiently use the wavelength resources and protect multicast traffic against any single-link failure,and it also can greatly improve the traffic restorability when multiple-link failure occurs.