Drucker-Prager yield criterion is widely used in rock engineering with the benefits of its simple form and clear physical meaning. However

its drawbacks are gradually revealed after years of research and application

such as lacking the effect of stress angle and the oversized tensile-shear region. Therefore

we propose a modified Drucker-Prager yield criterion in this study. In compressive-shear region

the same form of Drucker-Prager yield criterion is reserved

but in tensile-shear region

the original conical surface is replaced by the combination of a spherical surface and a cross section. This method can not only consider the real tensile strength of rock

but also satisfy the condition that the yield criterion passes the point of uniaxial tensile strength. A corner model is introduced to describe different strength characteristics of rock under triaxial compression and triaxial tension. To satisfy the condition that the yield criterion goes through the point of uniaxial compressive strength

a new method for calculating the value of k is suggested. Then the calculated results of the yield criterion are further fitted with that of true triaxial tests to verify the applicability and accuracy of the modified yield criterion. By comparing the results of the modified criterion with that of Mohr-Coulomb criterion

it is shown that the modified yield criterion can describe experimental data well

which is more realistic than the later.