The main purpose of this study is to apply regression analysis to build the relationship between flow rate and differential pressure by modeling through experimental data, and specifically use such relationship in interpreting the flow rate of air conditioning water system, in order to establish a lower-cost alternative flow rate interpretation of which the information obtained is more conveniently. For the experimental way, we installed pressure transmitters and paddle wheel flow meters in the condenser side of the chiller, air-handling unit and in the inlet and outlet ends of pump of a small air-conditioning system respectively, and then recorded the values of such device as the pump, the air-handling unit and the condenser under different use conditions as a single pump operation, multi-pumps operation in parallel, and multi-pump operation in variable frequency, to carry out the modeling of relationship between differential pressure and flow rate by actual operation data, and analyze the results. From the experimental results, the modeling equations obtained by the air-handling unit and condenser ends are applicable to a single pump operation, multi-pump operation in parallel and multi-pump operation in variable frequency. The differential pressure obtained to interpret flow rate has a high accuracy and the error value is less than 2%. According to the study results of this experiment, the convenience of flow rate interpretation can be significantly enhanced to facilitate the formulation of air-conditioning energy-saving strategy.