Abstract: In the construction of tunnels of small and medium water conservancy projects in our province, it is rare to encounter gas. Therefore, once encountered, there are not enough treatment procedures and methods that can be used for reference. Through the analysis of the entire process from the discovery of gas to the commissioned inspection, the selection of units, the implementation of treatment, and the acceptance of the Sanyangxi Tunnel of the Shaba Reservoir, it not only ensures the compliance of the procedures, the safety of the implementation process, but also reduces the investment. Water conservancy projects encountered similar problems and provided a relatively complete experience.