Abstract: The quantitative recognition of potential earthquake sources has been studied by fuzzy-reasoning and power mode of thinking,that is,synthetic consideration of various factors at the same time. As an example,the North China region has been analysed. Results indicate that the method reflects our present knowledge of the characters of earthquake tectonics,seismicity and potential earthquake sources; considers synthetically the influence between factors,and gives the results in digital expression. Thus a foundation for determining the parameters of earthquake sources is laid. Therefore the method is scientifically sound and practical.