In this study, an observer based indirect adaptive fuzzy controller for the anti-lock braking system (ABS) is proposed. First, using the Lugre internal friction model in the single corner model of automobile, road profile is estimated. Then, using the estimator results, the optimum slip is estimated. It should be noted that in the optimum slip, the maximum longitudinal friction created between the tire and road is achieved, so that the automobile stops in the least possible distance. Since some of state variables of the system are difficult to measure or contaminated by noise, and observer based controller is designed in this paper. The controller objective is to realize the reference slip obtained from the road condition estimator. Using Lyapunov stability theory, it is verified that the values obtained for road condition and vehicle speed will converge to their actual values. In addition, it is shown that the indirect adaptive fuzzy controller results in asymptotic tracking of the optimum slip. Simulations results show the proper performance of the proposed anti-lock breaking control system in achieving the optimum slip and quick stop of the car without locking the wheel in various road conditions.