Abstract: Based on the multimode theory and ray theory of electromagnetic wave propagation in coal mine tunnels, the paper established a wireless channel model of wireless signal in mine tunnels, deduced formula of coherence bandwidth of wireless channel considered to important parameters influenced by the coherence bandwidth, such as propagation distance, tunnel section size, carrier frequency, antenna polarization, antenna location, medium electrical parameters. It simulated influence of the above parameters on the coherence bandwidth in a rectangular tunnel with width 4 m, height 3 m, and obtained theoretical results that the coherence bandwidth of the mine channel is proportional to the frequency, inverse proportional to propagation distance, the tunnel section size and the relative medium electrical parameters, to change position of antenna in the rectangular section tunnel is less influenced on coherence bandwidth.