Recent years, Orthogonal Frequency Division Multiplexing (OFDM) has been widely applied to various digital communication systems. WiMAX (Worldwide Interoperability for Microwave Access) holds a combination of fixed and mobile broadband wireless access techniques. IEEE 802.16e is the specification designed for WiMAX system in application of mobile environments. In order to achieve robust performance, one of the most important steps is the channel estimation procedure based on limited number of pilot signals. Owing to the channel's time variant characteristic caused by user's mobility and irregular arrangement of pilot signals in 802.16e system, the exact channel estimation is more difficult to achieve for this system. In this paper, under the consideration of the effects of mobility and AWGN, we propose a DFT-Based OFDM channel estimation scheme for the WiMAX systems. Simulation results show that the proposed adaptive channel estimation scheme can keep good system performance.