Abstract: In this paper, an algorithm is proposed for mobile robot to follow walls. Firstly the wall shapes of the indoor environment are classified into different types for which wall-following strategies are designed respectively. When the mobile robot moves, the wall-following status changes, based on Finite State Machine(FSM), then the corresponding wall-following strategy is chosen to control the mobile robot. Experiments on the Pioneer 2DX mobile robot are conducted to evaluate the performance of the algorithm, and good results are obtained.