It is stated, on basis of analysis on the blasting theories at home and abroad, that parameters, such as vibration velocity and vibration time should be introduced to analyze the influence of blasting on the surrounding structures. In the paper, the influence imposed by the blasting excavation of tunnels with extralarge crosssections is simulated, with Guanziling tunnel on LanzhouChongqing railway as an example.  The study results indicate that the stress on the inverts toward the blasting side is the largest; as time goes on, the maximum tensile stress on the upper existing tunnel occurs at the invert, arch foot and crown toward the blasting and the wall backward the blasting in succession; the strength of the stresses varies from weak to strong, then varies from strong to weak and in the end vanishes gradually. A series of vibrationreducing measures are proposed on basis of the study results. The paper can be served as reference for similar projects in the future.