Abstract: The paper researched timing synchronization of mine through-the-earth communication system. It built a simple elastic wave medium model of earth channel firstly and obtained multi-path delay of the model is 20 ms through calculation. Then it simulated, analyzed and compared application performances of data auxiliary timing synchronization method and non data auxiliary timing synchronization method in the through-the-earth communication system by use of Matlab, and got following conclusions: the non data auxiliary timing synchronization method requires high signal power of the through-the-earth communication system, and the data auxiliary timing synchronization method has higher reliability and is fitter for the through-the-earth communication system. Finally, it simulated decoding error rate of the through-the-earth communication system which used the data auxiliary timing synchronization method under the condition that length of cyclic prefix of OFDM was 0.5, 2, 4 times of the maximum delay time separately and SNR was from 0 dB to 18 dB. The simulation result showed that the decoding error rate of the through-the earth communication system achieves 10-5 order of magnitude when the length of cyclic prefix of OFDM is above 2 times of the maximum delay time and the SNR is above 16 dB, which verifies application reliability of the data auxiliary timing synchronization method in the through-the-earth communication system.