Abstract: Mohr-Coulomb and Hoek-Brown failure criteria are the two most widely used failure criteria in rock engineering. To simulate brittle failure of rocks in deep tunnel, models based on these two failure criteria have been proposed, including the Cohesion Weakening and Friction Strengthening (CWFS) model, the Damage Initiation and Spalling Limit (DISL) model and the Brittle-Ductile-Plastic (BDP) model. However, because of the issues of strain hardening under high confinement and large ambiguity in model parameter determination, these models face limitations in practical engineering application. Based on progressive failure of rocks, we found that cracks propagate under compression and as a result the Geological Strength Index (GSI) decreases with the increase of plastic strain. By defining the GSI value as a function of plastic strain, a strain-dependent GSI softening model based on the Hoek-Brown failure criterion is proposed. This model is then implemented in FLAC 3D to simulate the triaxial compression test of T 2b marble in Jinping-II hydropower station. It is found that this model is able to simulate the mechanical behavior of the brittle-ductile transition observed in the triaxial compression test of the Jinping marble.