Because of the maturation of the VoIP technique, VoIP can not only satisfy the basic requirement of telecommunication but also provide multimedia communication services. As a result, it is very attractive in recent years. Through VoIP, the cost of communication can be saved. It can be very competitive. In addition, VoIP can be combined with PSTN (Public Switched Telephone Network). This helps traditional PSTN users to be able to use traditional telephones to make VoIP calls.Besides, VoIP can also extend other services. It can achieve diversification of services, comfortable using and reducing the cost requirement. Moreover, with the increasing of the VoIP population, the traditional method using single server is unable to afford so much loading. It is possible that the large load makes the service stop anytime. This makes the usability and the reliability decrease. To make the VoIP service work anytime, we implement a method in both client side and server side to achieve the goal of continuous providing of the service. From this implementation, the service of VoIP can be provided anytime. The users, however, have no need to be aware of the different operation style in VoIP.