Abstract: A normal fault with 18 m separation is exposed in 2313 working face in Jincheng Coal Mine, but the extension status is not clear. The fault may have an effect on the safety mining. Based on the reflection and transmission method theory of in-seam wave and the site survey observing, system arrangement form of double tunnel is used to explore. Taking the reflection method as the principal thing, and transmission method as a supplement, the reflecting interface and the extension status of large fault in 2313 working face are explored. The results indicate the extension status of large fault is ascertained through reflection method in the two tunnels of 2313 working face. The exploration results of reflection method are identical with the attenuation coefficient CT results of transmission method. The positional deviation of fault is less than 10 m through drilling verification. Therefore, aiming at the large fault along with the strike of working face, the reflecting interface of hanging wall and footwall can be explored through reasonable arrangement form of observing system.