By analyzing the principles and shortcomings of traditional simulated annealing algorithm，an im-proved simulated annealing algorithm was proposed.To avoid missing current optimal solution，the new algorithm memorizes current best solution，and it also sets up dual-threshold to reduce the amount of calculation while maintaining optimality.After taking serious insights into spectral shape multiplexing and Simulated Annealing，an efficient energy increment calculation method was designed to speed up calculation.The results of simulation and experimental verify that the new algorithm converges faster and better than the traditional simulated anneal-ing algorithm in solving the spectral shape multiplexing technique.