Abstract: The Mohr-Coulomb criterion has been widely used in the finite element analysis of geotechnical engineering. Previous studies have shown that modified Mohr-Coulomb criterion proposed by Abbo-Sloan has better numerical stability than the traditional one. However, most general finite element programs do not provide the constitutive model based on the modified Mohr-Coulomb criterion. Furthermore, most subroutines for this constitutive model suffer from insufficient numerical accuracy and stability. A new stress updating algorithm for the modified Mohr-Coulomb criterion was thusly proposed, the formulas for calculating the parameters were derived, and the implementation scheme was provided. A UMAT subroutine was developed with ABAQUS as the platform. The UMAT subroutine was tested by a triaxial compression case and by a geotechnical engineering slope stability analysis case. The results indicate that the UMAT subroutine has a high numerical accuracy and a satisfactory convergence performance.