In this paper, we consider the slip ratio control when braking as with anti-lock braking system and propose a discrete-time slip ratio control method using discontinuous input which chattering phenomena does not occur and preserves the robustness of discontinuous input. Firstly, in order to design a discrete-time controller, the discrete-time slip ratio model is derived by using Euler approximation since the slip ratio dynamics represents nonlinear system. Next, based on the discrete-time model with respect to slip ratio, a discrete-time slip ratio controller which chattering phenomena does not occur is derived and the stability of the control system is proven by stability theorem of discrete-time system. Finally, The effectiveness of proposed control method is verified by numerical simulation.