Based on central air conditioning system of Xi'an-Xianyang international airport, energy efficient utilization with life cycle theory and analytic hierarchy process was conducted. Firstly, the application of life cycle and analytic hierarchy process to building energy was deeply studied. Secondly, life cycle inventory analysis was conducted combined with the practical cases data. And the data resource is related to the proposed model. Thirdly, On basis of analytic hierarchy framework model and analysis of energy consumption as well as potential environmental impact on air-conditioning project, the study on how to evaluate energy-consumption project with the use of life cycle impact assessment is done. Based on the life cycle assessment of practical cases data, a new hierarchical evaluation model of energy utilization is put forward. And in view of the model， several suggestions are given such as establishing energy utilization process monitoring and evaluation from the point of whole life cycle assessment. This provides a theoretical basis for policies about enormous quantity of building energy and energy saving of air conditioning system.