Abstract: The concept and construction method of maximum selectivity curve is presented in this paper.In the view of physical concept,any points in the curve represent the state point of the maximum selectivity corresponding to the feed point ( x 0, y 0, z 0).To reach the maximum selectivity curve from the feed point the CSTR process should be selected.According to the property of the maximum single yield curve and maximum selectivity curve,the attainable region can be divided into three sections,that is ,the continuous stirred tank region,PFR region and non-operation region.Among which the area of continuous stirred tank region would change with the kinetic conditions and even disappear completely,while the non-operation region will not exist when the parallel reaction is concerned.Based on the property of different region in the attainable region and the connection boundary,the region dividing strategy for reactor network synthesis is put up.By this strategy,it is convenient to draw up the flow structure of the reactor network to achieve the optimal object of waste minimization.