Abstract: Presented an iterative receiver for joint channel estimation, data detection and decoding over a time-varying frequency-flat Rayleigh fading channel. First, a factor graph (FG) that represents a joint posteriori probability mass function of the information bits and channel coefficients given the channel output was established. Then the sum product algorithm (SPA) was implemented on the FG in the proposed algorithm. Gaussian parameterization was employed to approximate the exact probability density function in message passing to yield a forward-backward recursion for the purpose of channel estimation. Compared with the traditional channel estimation and decoding methods, the effectiveness of the proposed iterative message passing algorithm is demonstrated through computer simulations.