In this paper we propose an agent architecture to improve the flexibility of videoconference systems with strategic-INTER knowledge. The proposed architecture achieves more flexibility by selecting dynamically the strategy of QoS (Quality of Service). To select the strategies, the systems have to take into the consideration of the properties of problems occurred on QoS and the status of problem solving process. This architecture is introduced as a part of knowledge base of agent dealing with cooperation between software modules of videoconference systems. We have implemented the architecture and our prototype system shows its capability of flexible problem solving against the QoS degradation, along with other possible problems within the time limitation. We confirmed that the proposed architecture can improve its flexibility of a videoconference system compared to conventional systems.