A semi-analytical solution of dynamic stress of arbitrary cross-section underground cavity in half-space for incident plane SH waves is presented using wave functions expansion method combined with boundary discrete method

and the numerical precision is validated in detail.Monte Carlo method is used to randomly generate 30 samples of variation coefficient 0.05 for cross-section shape of the cavity

and the effect of cross-section shape on the dynamic stress peak（DSP）is studied by statistical analysis.It is shown that

cross-section shape has significant effect on the DSP around cavities in half-space.The maxima of the DSPs are much larger than those of its relevant peaks of the analytical solutions of the circular cavity

with the maximal value being increased by 60%

and the averaged value being increased by 24%;the variation coefficient of the DSP may be up to 3.5times greater than the variation coefficient of the cavity radius.