A chattering-free integral sliding-mode control method is proposed for the discrete-time linear systems with unmatched uncertainties. Based on the linear matrix inequality(LMI) technique, a new switching function and a sliding- mode controller are proposed to minimize the effect of unmatched uncertainties, and the Lyapunov stability is proved. The saturation function is introduced to ensure that the system states move in a small neighborhood of the sliding surface as quasi-sliding motion. The boundary layer thickness of the saturation function is chosen to make sure the controller chattering-free with strong robustness. The results of theoretical analysis and simulation show the effectiveness of the proposed integral sliding-mode control scheme.