The NC grinding of Si3N4 ceramics rotary curved surface workpieces was carried on the CNC jig grinders, combining the nomal tracing grinding and the arc envelope forming grinding. According to the grinding track, a grinding surface scallop height model was built. The model analysis indicated that workpiece curvature, wheel radius and feed rate affected the surface roughness. A prediction model based on the response surface methodology (RSM) was built to study the influences of these processing parameters on the surface roughness, using the Box-Behnken design to design the grinding experiments. It was shown that the surface roughness of rotary curved surface workpieces grinding which increased with increasing workpiece curvature could be reduced by chosen larger radius wheel and lower feed rate. The confidence and practicality of the prediction model is high in experimental conditions. The process parameters can be selected to improve the quality of the surface based on the model of the paper.