As previous heuristic p-cycle capacity allocation algorithms fail to consider the limitation of link capacity

we propose a new heuristic algorithm.On the basis of spare capacity

this algorithm constructs a p-cycle by taking the maximum working capacity as the expansion standard and uses the constructed p-cycle for capacity allocation and uses COST239network topology for algorithm simulation.The simulation results show that this algorithm can use less spare capacity to protect more working capacity and reduce the number of p-cycles.