Abstract：Based on rock geological data of a large cavern under high in-situ stress，the effects of three arch shapes，single center arch and three-center arch and elliptical arch，of large caverns under high in-situ stress on stress effect in rockmass of arch are analyzed by the elastoplastic finite element；The results reveal that this effect is very obvious，and some stress concentration factor reaches 3.33；whichever arch shapes are adopted，stress intensity neighborhood of arch seat is unavoidable. Gray condition criterion is developed with plastic region and stress concentration factor；and each gray condition value is calculated. According to gray condition value，by synthetically judging，no matter what in-situ stress side pressure coefficient is，the elliptical arch is the best with the three-center arch the second.
