Vacuum Circuit Breaker (VCB) consists of the main frame with the operating mechanism and the main circuits including VI (Vacuum Interrupter). Especially, a VCB for the generator protection, which is used in a power plant, requires very large contact spring force because it has to be able to withstand the high short circuit current. In order to release closing energy of VCB, the cam type mechanism using extension spring as energy source is applied. In this study, the prototype generator VCB has been designed and its analytical multibody dynamic model using the Recurdyn has been developed. Based on the simulation result of analytical model, the required design variables of generator VCB are determined. To verify the analytical model, the prototype VCB sample has been manufactured. The dynamic characteristic of prototype VCB sample is also measured and compared with the analytical model.