Abstract: High stress and high ground pressure of rock mass under extreme environment in deep mining are the main factors affecting engineering safety. This study points out that the Mohr–Coulomb criterion (M–C criterion for short) cannot judge the yield failure of rock materials under high hydrostatic pressure. The triaxial compression experiments of rock samples under high stress were carried out to observe the failure phenomenon of rock materials under high hydrostatic pressure, and the developed equation of M–C criterion under high hydrostatic pressure was derived. The results show that, different from the existing M–C criterion, the shear strength decreases gradually when the difference between axial and confining pressures increases to a certain peak value, and rock samples can also yield failure under high hydrostatic pressure. The developed equation of M–C criterion is in principle consistent with the experimental results. Meanwhile, the lower limit of M–C yield surface under low hydrostatic pressure and the upper limit of M–C yield surface under high hydrostatic pressure are discussed. The research results can provide theoretical reference for the safe and efficient development of deep engineering.