Abstract: To increase flexibility and autonomy in slot exchanging and make best use of airport resources,a dynamic slot trading method is introduced based on MAS(multi-agent system) coordination to exchange slot in ground delay programs under collaborative decision making(CDM GDP).Using market mechanism based coordination strategy,a slot trading mechanism with conditional auction based on slot credit substitutions(SCSs) is established;a slot trading model with MAS coordination is presented,which give airlines flexibility to choose the trading partners.Under the BDI(belief,desire and intention) -based reasoning coordination mechanism,a utility-based internal reasoning strategy of airline operations center(AOC) agent is designed,and the process of the utility calculation is described.A simulation system of the proposed method is developed on the Microsoft.NET platform,and some typical CDM GDP instances are used for the simulation and comparison to verify the method.