Abstract: Abstract: Considering the difficulty of traditional symbol timing recovery at the extremely low/ low signal-noise-ratio (SNR) in the deep-space communications, an iterative symbol timing recovery method based on non-binary LDPC coded modulation system is proposed. This method can estimate and correct random time delay over the symbol period by combining Mueller and Muller timing error detector with iterative decoding method. According to the type of message feedback from the LDPC decoder, two different kinds of iterative timing recovery strategies are presented, and they are separately based on hard decoding feedback information and soft decoding feedback information. Simulation results show that the symbol timing synchronization algorithm based on these two kinds of decoding feedback information both achieves pretty good performance under the condition of low SNR, random time delay and high-order modulation, and they performs fast convergence, which is of powerful practice. Furthermore, symbol timing synchronization algorithm based on soft feedback decoding information performs better, because it keeps more complete probabilistic information.