Abstract: Considering the heterogeneous property of rock mass, astatistical constitutive model is developed and is implemented in LS-DYNA byusing the user defined material subroutine. In the constitutive model of therock mass, a two parameter Weibull's distribution is used to simulate thestatistical properties of the tangential modulus and the strength of therock mass. The rationality of the model is demonstrated by a numerical test.