Embodiments of the present disclosure relate to methods, devices and medium for controlling a water chiller in a central air conditioning system. The method comprises acquiring a current prioritization rule when a to-be-started water chiller in a central air conditioning system needs to be started; determining a plurality of data each to-be-started water chiller respectively associated with one or more of the plurality of prioritization dimensions; adjusting a ranking order of the plurality of prioritization dimensions based on the acquired plurality of data to obtain an adjusted prioritization rule; ranking the plurality of to-be-started water chillers based on an adjusted prioritization rule; and determining, based on a final ranking result of the plurality of to-be-started water chillers, a currently most suitable to-be-started water chiller so as to control to start the determined a to-be-started water chiller. Thus, a prioritization rule can be dynamically adjusted, and a currently most suitable to-be-started water chiller can be quickly and accurately determined.