In this study, a frequency converter was used to carry out variable frequency control to the compressor with constant frequency of a small 3RT central air-conditioning air-cooled chiller, but the indoor blower and cooled water pump were still kept by constant frequency operation. It is to explore the energy-saving effect of chiller compressor and the cooling fan after being carried out the variable frequency control, on the premise of PMV, the index of thermal comfort, set to 0.5. The experimental results indicated that under constant frequency operation, the average power consumption of compressor was 2.62kW and the average power consumption of cooling fan is 0.33kW; under variable frequency operation, the average power consumption of compressor is 2.38kW and the average power consumption of cooling fan was 0.29kW. After variable frequency control, the compressor could save 9% power consumption, and the cooling fan could save about 14% power consumption, with remarkable energy-saving results.