This paper describes a novel numerical simulation method for simulating interfacial dynamics of a single bubble rising in liquid lead bismuth alloy. Numerical simulation of a single nitrogen bubble in liquid lead bismuth alloy from static to the full development of dynamic behavior based on diffuse-interface method was done to get the relationship of rising velocity and deformation of the bubble by time. Results of simulation of the flow characteristics of inert gas and liquid LBE alloy based on diffuse-interface method are consistent with the Grace emperical relationship graph, which verifies the feasibility and the accuracy of diffuse-interface method on simulation of rising bubble’s behavior in liquid LBE alloy. It is easy to find that with the increase of Eo, which is determined by bubble initial diameter when fulid is determined, the bubble deformation increases, and the bigger the bubble is, the easier it is to split the sub bubbles.