U-Ra equilibrium coefficient is a geophysical parameter which characterizes the uranium-radium equilibrium state of uranium ore samples. It has great significance for accurately estimating the uranium resources of ore districts and evaluating the uranium mineralization potential of the study area. This study claryfys the definition and calculation method of U-Ra equilibrium coefficient, discusses the factions and influence of U-Ra equilibrium coefficient in uranium exploration process, as well as the characteristics of U-Ra equilibrium coefficient of different types of uranium deposits. Here the author emphasizes that the essence of causing U-Ra disequilibrium is the redistribution of uranium or radium within one equilibrium period of the uranium series (about 1.9 Ma), and analyzes the potential reasons for sample deviation from uranium or radium.