This paper proposes a delay-dependent guaranteed cost control scheme for engine idle speed control (ISC) with induction-to-torque delay and external load disturbance.An augmented linearization model of engine at idle speed operating mode was developed based on physical principle and experiment data.To provide a compromise between disturbance rejection and other performance requirements of ISC,a multi-objective cost function upper bound was given,which can help us to take into account the fuel economy and disturbance rejection performance together in ISC.Poles constraint was added to the closed-loop system to guarantee convergence rates of state.The whole optimization solution to ISC can be solved under the framework of LMI.A commercial engine model was utilized to assess the performance of the controller.Simulation results on this model show us that designed controller can achieve desired performance.