In this paper, the method to design the reduced-order switching function for an uncertain linear system in special coordinate basis (SCB) form is proposed. The sliding mode control with this method guarantees the asymptotic stability of all the states of system in presence of matched disturbance. The proposed design method is applicable to the system with unstable internal dynamics as well. This method enables the option of designing the control law with reduced-order states that are involved in the design of switching function. Also, a high performance sliding mode step-tracking control for non-minimum phase systems using reduced-order nonlinear switching function is proposed. The method is also extended to multiple-input and multiple-output (MIMO) systems. An effectiveness of sliding mode control with reduced-order switching function is shown through numerical examples.