This paper is concerned with the channel estimation for orthogonal frequency division multiplexing interleave division multiple access (OFDM-IDMA) systems in the presence of time varying channels. Although the estimation of the channel state information (CSI) for OFDM-IDMA systems is investigated by current literatures in slow fading channels, the channel estimation in the context of fast fading environments remains a challenge, which focuses on a desired tradeoff between the amount of pilot symbols and CSI estimation accuracy. For alleviating the above problem, in this paper, we develop a class of data-aided channel estimation schemes based on the log-likelihood ratio(LLR) calculation at the receiver to track the channel variations for OFDM-IDMA systems. Simulation results demonstrate that the proposed data-aided channel estimation scheme offers substantial performance gain over its conventional counterparts especially in the high-mobility case.