In order to develop high efficient modeling methods and general analysis software for multi branch torsional vibration systems, taking a one-shaft system with multi-rotors as an example, this paper explored the dynamics modeling, equations and the solving procedures. According to the compatibility conditions at a junction, dynamics modeling ＆ its solution of multi branch torsional vibration systems were studied. And then, the methods and algorithm were expanded to the multi-junction ＆ multi-branch torsional vibration systems. Based on the above research, a general analysis software was developed that can be used as a high efficient analysis tool for tosional vibration systems. The above method and software were tested by an example.