Grinding stability was analyzed concerned with contact deformation and contact stiffness of wheels. Elastic deformations of the grinding wheel were measured with inductance sensors. Dynamic grinding system model was set up. Relation between contact stiffness and chatter growing index was analyzed. Chatter suppression experiments with variable grinding speeds were carried out. When wheel is in contact with a workpiece, contact deformation can occur. The contact stiffness of grinding wheel is a variable. The relation between chatter growing index and contact stiffness is an increasing function. Chatter growing index can be decreased by lowering contact stiffness of wheel. The grinding system stability will be improved with variable grinding speed.