Free vibration analysis is the foundation of dynamic seismic analysis for underground structures. The effect of soil elastic parameters on the free vibration of long large cross section underground structure is studied on the basis of the vibration equation of linear underground structures derived by the authors previously.Parameter study shows that in general wave propagation velocities in the structure increase with soil elastic parameters.But the influence of Winkler’s parameter k is significant

while the effect of the second soil elastic parameter gP is insignificant.Free vibration frequency of underground structure increases with relative wave number and soil elastic parameters.Differing from the influence of soil elastic parameters on wave propagation velocities

the influences of soil elastic parameters k and gP on vibration frequency of underground structure have the same order

therefore the influence of the second soil parameter gP on free vibration of underground structure should not be neglected.