The curve NC grinding methods in presnet are analyzed. On the basis of this, a new curve NC grinding method―region contact grinding (RCG) method is proposed. With this method, the contact point between grinding wheel and workpiece can be controlled in the given contact zone. The problom of grinding wheel's distortion which is produced by contact point excessively deviating from symmetrical central plane of grinding wheel can be overcome. In order to the grinding mode, a new interpolation algorithm―region equiangular linear interpolation (RELI) is proposed. Namely, in terms of the convex-concave property of processing curve, some grinding regions are divided. In each grinding region, the grinding wheel's swing angle within each interpolation cycle is evenly distributed. Thereby, in the process of grinding a convex-concave curve, grinding wheel's contact points totally locate in the range of contact zone angle.