Time synchronization is a crucial component of WSN. As the rapid development of mesh network, firefly-inspired synchronization algorithm comes out for solving the synchronization issue of large-scale networks. But it usually has a short cycle for improving the sync rate. In this paper, a multiscale cycle synchronization strategy is proposed based on firefly-inspired algorithm for long cycle. First, the firefly model used in our strategy is introduced. Then a description is proposed about the multiscale cycle synchronization. Simulation results show the great acceleration on sync rate and the improvement of stability.