Focusing on the deficiencies in production line balancing of present methods, a new method named production line's dynamic balancing method, which combined heuristic method and visualization simulation together, was proposed. In this method, a double-objective model of line balancing was built up, which ensures the number of workstations and the smoothness index are both minimum. Then an improved particle swarm optimization algorithm was used to solve the problem. The production line system is suitable to build its visualization simulation model by the simulation software of Witness. At last, an instance of this method was discussed.