There are many schemes of residential central air conditioning systems for selection， the selection is affected by many factors， the reasonable selection of evaluation indexes is the key factor for the proper option. In this paper， in order to evaluate the performance of the whole system synthetically， the gray comprehensive evaluation method is introduced and used， the mathematical model for optimization and selection of air conditioning schemes is established， and with an example of residential building in Beijing the index values of chosen six air conditioning systems are calculated and optimized. The schemes are the air-source heat pump system， household gas-fired air conditioning system， air-cooled chiller unit/gas-fired boiler system， water loop heat pump system， ground-source heat pump system and solar heat pump system. In the process of optimization calculation， the aspects of economics benefits， energy saving， environment protection and system reliability are taken into account. According to the calculation results， the water loop heat pump system is proposed to be optimal option under the given conditions.