This thesis use standard IEEE 802.16e-2005 to make platform for simulating decoded performance when Mobile WiMAX Down Link system under the channel has velocity. While wireless transmission, WiMAX signal will be disturbed by a lot unknowable noise and multi-path. For receiving correct data, we need using channel estimation to offset channel fading and then get original data by decoder. The platform use channel model is established by ITU-R. This thesis compare the decoded performances, which are simulated by using QPSK, 16QAM, 64QAM under different velocity channels and offset by two Dimensional linear interpolation or iterative channel estimation.