In order to solve the problem that fire spreading is difficult to control and oxygen deficiency in a tunnel is insufficient when a fire disaster occurs, the invention provides a tunnel fire extinguishing system. The system mainly comprises a high-position water pool, a water supply pipeline located at the top end of the interior of the tunnel and a water supply air guide pipe connected with the portion between the high-position water pool and the water supply pipeline, wherein the high-position pool is located above the tunnel, a plurality of spray heads uniformly arranged along the length direction of the tunnel are connected to the water supply pipeline, a plurality of air guide pipes are arranged on the water supply air guide pipe, and a one-way valve used for controlling fluid to be only fed is arranged in the water supply air guide pipe.