With the increasing popularity of multimedia streaming applications, a Web-server usually overloads in heavy-request period. A scheme of Web-server cluster has been widely employed to provide high-efficiency Internet services. In this paper, a switching difference control method is proposed to dynamically distribute the traffic among the N Web-servers. An TV-tanks system is suitable for modeling a Web-server cluster to address the traffic-balancing problem. The proposed switching policy is based on a subsystem consisting of two tanks, called tank-pair. Based on some feedback policy, different tanks are dynamically chosen to form the tank-pair so that all the TV tanks can be controlled in a time-sharing manner. A switching rule, called first-targeted-and-then-round-round-switching (FTRRS) Rule is introduced. Some simulation results for the FTRRS rule are reported in this paper, and they show that the proposed method is effective.