Profile control/water plugging is an important approach to increase production. Reasonable treatment radius and the volume of blocking agent are essential parameters not only in profile control/water plugging engineering but also in the area of reservoir simulation. Traditional calculation method used for treating layer only is derived by Darcy's equation. However, traditional calculation method neglect the influence of multilayer characteristics, which may lead to erroneous results. In this research, a new calculation method about profile control/water plugging is derived by considering the influence of multilayer characteristics. In order to derive this equation, layered-parallel beds model is established and ideal Darcy's radial flow theory is applied. In the new calculation method, treatment radius depends on desired effects, water plugging effect and multilayer characteristics. The scheme proposed by using the new calculation method is evaluated by using data from block SH2 in the HeNan oilfield. Calculation results show that the variation of treatment radius is generally in good agreement with actual situation.Introduction.