The invention provides a three-party video conference system and a method. According to the three-party video conference system of the invention, a second terminal device which can be transmitted under different protocols can be used for receiving and transmitting compressed digital signals coming from a first terminal device and a third terminal device. Therefore, even when the first terminal device and the third terminal device can not mutually transmit the compressed digital signals under the same protocol, the subscriber can use the three-party video conference system and the method of theinvention to realize the application of the three-party video conference.