The previous chapter conducted an in-depth study on the hysteresis characteristics of the medium in the pipeline network and the system nonlinear characteristics. The results show that both the temperature and flow rate of the medium exhibit hysteresis characteristics during the response process, which dynamically change with the system configuration and control actions, affecting the overall performance and control effectiveness. With the increasing demand for intelligent HVAC control systems, the periodic optimization is no longer sufficient to adapt to complex and variable operating conditions, often resulting in untimely or unnecessary optimization actions that impact system performance. Therefore, determining the optimal timing for system optimization and control during the process is crucial to enhance the adaptability of the variable flowrate HVAC system to operating conditions. This chapter will present a nonlinear optimization method by combining with medium hysteresis characteristics and system nonlinear characteristics, to enhance the overall stability of the HVAC water system and its adaptability to random operating conditions. Additionally, experiments will be conducted to compare the performance of the proposed method with the traditional method in actual systems, comprehensively evaluating the two methods in terms of decoupling effect, control effectiveness, and energy consumption.