Abstract: In order to know the mechanical effect and the stability of the adjacent gas pipeline,the optimum elastic modulus scheme of the loose soil,grouting reinforcement soil and primary support are back-analyzed with utilization of the orthogonal experiment design and on the basis of in-situ measured deformation.The safety impact evaluation on the gas pipeline during the construction process of the hydraulic tunnel are carried out with the back-calculated optimum parameters.The results show that the elastic modulus values for the primary support,the grouting reinforcement soil and the loose soil are 26000MPa, 50MPa and 40MPa,respectively.The adjacent gas pipeline was safe and stable during the construction process of the hydraulic tunnel.