This paper focuses on the rotor system with loose support fault as the research object. A mechanical model of the 6-mass, 12-degree-of-freedom faulty rotor system is established. Nonlinear dynamic characteristics of the system are extracted by analyzing the variation of the support mass through numerical methods. Furthermore, the bifurcation characteristics and routes to chaos of the system are investigated. The results indicate that when the support mass of the loose faulty rotor system varies, the system exhibits complex nonlinear dynamic behaviors. The conclusions drawn provide a theoretical foundation for fault diagnosis of this type of rotor system and ensure its safe operation.