Abstract: In view of the characteristics of frequency-dependent rejection (FDR) calculation in the field of electromagnetic compatibility analysis, such as partial theoremization, insufficient computational accuracy and operability, a FDR calculation method based on Gauss-Lesson integral algorithm and its related software is introduced. Compared with the commonly used calculation methods, the software has the characteristics of high calculation accuracy, simple operation and strong practicability. The typical case studies are used to illustrate the method, which can provide effective support for radio managers in the interference analysis of Global Satellite Navigation System (GNSS).