Abstract: Electromagnetic interference is one of the important factors affecting the reliability of monitoring system of hydropower station,which will affect the safe and stable operation of hydropower station. In order to solve the above problems,this study analyzed the electromagnetic interference detection method of hydropower equipment in consideration of small signal stability. Firstly,the identification method of electromagnetic interference small signal stability characteristics is analyzed,and the UHF method and high frequency current method is used to find small signal characteristics for the collection of interference signals. Secondly,the scheme of collecting electromagnetic interference signals is studied based on the establishment of data acquisition cards and its correlation with small signals. Thirdly,the electromagnetic interference signals are classified,and the detection platform is simulated according to different levels of electromagnetic interference signals to match the corresponding detection simulation platform. Then,the small-signal stable data is accurately recorded. Finally,a comparative experiment is used to verify that the electromagnetic interference detection method based on small-signal stability has improved detection accuracy by about 3.5% compared with the traditional method,which is a hydroelectric power station. The results of this research serve as a more accurate solution to electromagnetic interference signals of equipment.