Abstract: The numerical simulation of a single nitrogen bubble in liquid lead-bismuth alloy (LBE) from static to the full development of dynamic behavior based on diffuse interface method was done to get the relationship of deformation and rising velocity of the bubble by time. Comparing results of simulation of the flow characteristics about inert gas and liquid LBE with Grace’s graphical correlation, it is found that deformation of the bubble is consistent with Grace’s graphical correlation, which verifies the feasibility and the accuracy of diffuse-interface method on simulation of rising bubble’s behavior in liquid LBE. By comparing rising behaviors of five different initial diameters of nitrogen bubble in liquid LBE based on diffuse-interface method, it is found that the smaller bubble initial diameter is, the disturbance will be more intense in the rising process, and the larger the bubble initial diameter is, the splitting phenomenon occurs more easily in the rising process.