In this paper, a time window mechanism based on the penalty value of route flap damping is designed to improve routing convergence. This mechanism judges the route stability in the network from BGP (border gateway protocol) routes correlation by observing multiple routes received from different peers jointly. Then BGP speaker can find instable routes earlier and makes stable routes get the chance to be selected earlier in route selection, thus curtail path exploration. Simulation results prove that with proper parameters this method can reduce convergence delay and communication overhead obviously. Furthermore, without addition information in BGP Update message, time window mechanism is a practical method to be deployed in the Internet.