Abstract: The appearance of complex large group brings new problems on the developing of group decision support system.Aiming at the complexity of developing of complex large group decision support system，this paper puts forward a kind of structure of group decision support system oriented complex large group.The system structure is guided by the decision problem solving.Firstly，design the decision problem solving process and method.Then，the system processing process is proposed.On the base of it，the layer and function structure of system is constructed.And its realization technology is studied in order to assist the developing of GDSS oriented complex large group.