Fuel economy can be improved by adopting the method of lean burning and reducing idle speed. And to achieve it, it is required to improve the performance of idle speed control. The dead time in the process of intake air control is one of the reasons, which cause the worse response and poor stability of idle speed control. The problem of the dead time compensation for intake air control is investigated in this paper. The Smith predictor and various linear compensators are discussed in it. By using a proper compensator, it is possible to improve the performance of the system's disturbance rejection. A new compensation method is presented in this paper, which is adopting a Smith predictor combining with disturbance compensator M1(s) and M2(s), to improve the idle speed control system's response to the disturbance at the front or rear part of the dead time. The simulation of idle speed control with the dead time compensation confirmed that the modified intake air control system is efficient.