In this paper an equivalent sliding mode control method of an induction motor speed is discussed. In this method the control signal consists of two parts: continuous and discontinuous one. Very good dynamical response of the drive system is obtained, which however is changeable with external and parametric disturbances occurring under different operation conditions. In order to ensure identical dynamic performance of the speed transients and system robustness during the switching line reach-ing phase, regardless of external and parametric disturbances, the time-varying switching line is pro-posed. The simulation results have been validated by experimental tests of the induction motor drive system.