Abstract: Aiming at the time delay problem in the control process of HVAC(heating,ventilating and air-conditioning),a method is proposed to overcome the effect of time delay when model parameters are changed.The adaptive algorithm of Smith predictor model parameters based on the first-order air-conditioning system model with pure delay time is deduced by signal relative theory and Lyapunov stability theory.In this algorithm,the Smith predictor can be adjusted on line to update the parameter in real-time on condition that the system model has changed.The adaptive algorithm Smith predictor is applied to air-conditioning system to avoid the instability and even oscillation caused by model parameters mismatch,solve the dynamic performance effect due to large time delay on air-conditioning system,and improve the stability of system.