To study the rock deformation with threedimensional model under rolling forces of disc cutter,by carrying out the circular-grooving test with disc cutter rollingaround on the rock,the rock mechanical behavior underrolling disc cutter is studied,the mechanical model of disccutter rolling around the groove is established,and the theory of single-point and double-angle variables is proposed.Based on this theory,the physics equations and geometricequations of rock mechanical behavior under disc cutters oftunnel boring machine(TBM) are studied,and then the balance equations of interactive forces between disc cutter androck are established.Accordingly,formulas about normalforce,rolling force and side force of a disc cutter are derived,and their validity is studied by tests.Therefore,a newmethod and theory is proposed to study rock-breaking mechanism of disc cutters. To study the rock deformation with threedimensional model under rolling forces of disc cutter, by carrying out the circular-grooving test with disc cutter rollingaround on the rock, the rock mechanical behavior underrolling disc cutter is studied, the mechanical model of disccutter rolling around the groove is established, and the theory of single-point and double-angle variables is proposed. Based on this theory, the physics equations and geometricequations of rock mechanical behavior under disc cutters of tunne boring machine (TBM) are studied, and then the balance equations of interactive forces between disc cutter androck are established. Accredially, formulas about normal force, rolling force and side force of a disc cutter are derived, and their validity is studied by tests. Before, a new method and theory is proposed to study rock-breaking mechanism of disc cutters.