This paper analyzed the feasibility of convert the constant flow hydraulic system to variable system in order to realize the regulating of the water flow rate in central air conditioning.The detailed design scheme,which uses transducer and industrial cornputer to implement the hydraulic system energy efficiency controlling for this projiect,is illustrated.The hardware system which uses transducer and computer is connected by RS-485.Software partially uses Visual(C++6.0) to compile the entire procedure.Result of the project proves the energy-saving effect of this control system.