Hongshiyan tunnel on Hefei～Wuhan passengerdedicated railway crosses Dabieshan mountainous area, which consists of metamorphic rocks. However, combustion phenomena are observed during the construction of the tunnel. The composition of the gases contained in the rocks is determined by means of insitu monitoring and chemical tests, on basis of which technological construction countermeasures are established for the gas tunnel. Due to the application of the technological construction countermeasures, the safety of the tunnel construction is guaranteed and good effects are achieved.