In this paper,characteristics of data centers and energy consumption status of their air conditioning systems are focused.Drawbacks of the allocation and operation mode of the air conditioning systems nowadays are pointed out.Local availability of natural cold source from fresh air and the energy saving potentials by directly introducing fresh air for indoor cooling are discussed.Importance and necessity of the directly introducing fresh air system used in data center air conditioning are expounded.A comparative schematic analysis on a model building of data center by design norm and simulation work has been done in this paper.Reasonableness and great energy saving potentials of the new style air conditioning system with directly introducing fresh air for indoor cooling has been well manifested by our research work.