The invention provides a method for controlling a global optimization of energy saving for a central air conditioning system based on a model, comprising a control module, a multichannel data acquisition card and control card, a refrigerating unit data collector and a controller, a humidity sensor, a temperature sensor, a flow sensor, a watt transducer, a water pump frequency converter, a fan frequency converter, an RS232/RS485 conversion module and a RS485/RS232 conversion module. The whole system can be operated under the condition of most energy saving according to an operating condition of optimized energy saving of each energy consumption device acquired by calculation of a calculation module by taking energy consumption modules of a refrigerating unit, a water pump and a fan and an ARMA air conditioning load forecasting model. The invention thoroughly concerns an influence of the operating condition of each power device in the system to the energy consumption of the whole system, takes a control strategy based on a forecasted air conditioning load, and performs an online update for the energy consumption modules of key energy consumption devices in the system, thereby greatly improving an effect of optimization of energy saving for the central air conditioning system.