High degree of reserve recovery disparities between layers is one of the main issues in multi-layer commingled reservoir at high water-cut stage. A correct understanding of inter-layer recovery degree has important guiding significance in making development decisions. Water injection profile data are important information that reflecting water injective behavior in different layers. Differences of water absorption capacity between different layers are mainly affected by reservoir petrophysical properties and remaining oil saturation. Based on hydropower similarity principle and non-piston type water displacing theory, a calculation method of inter-layer average remaining oil saturation in multi-layer commingled reservoir was established using water injection profile data. According to the results of numerical simulation, the relative error of the calculated results based on this method is less than 5%.