In view of the long time taken in using the classical p-cycle capacity assignment algorithms

this paper presents a fast heuristic one.Which constructs the p-cycle by taking the improvement of the protection efficiency of the p-cycle as the standard for its expansion and then carries out capacity assignment.As it is not necessary to construct in advance a candidate cycle

it can reduce redundancy and calculation time.The results of simulation on the basis of the pan-European COST239 network topology show that this algorithm can raise the network resource utilization ratio and greatly cut down the running time.