Tunnel boring machines (TBM) has been popularly used for rock tunnel constructions. It is of great importance to establish an accurate and reliable performance index of the disc cutters for the TBM, especially in complex ground conditions. The present study adopts smooth particle hydrodynamics (SPH) which is a virtual particle based meshfree method to evaluate the rock cutter performance in jointed and mixed media. The SPH method is capable of simulating rock crushing, rock fragmentation and chipping, etc., free of the mesh constraint of the traditional FEM and FDM models. A modified Drucker-Prager strength model for rock is developed. The nonlinear strength envelope of the developed model is generalized based on the widely accepted Hoek-Brown rock failure criterion. The performance of the rock cutters is evaluated in terms of rock strength index. The result will be useful for estimation of the attainable penetration rates and optimization of the cutters and overall TBM design.