The single-degree-of-freedom two-rotor system, as the most classical self-synchronous system, is widely used in engineering. In this paper, a dynamics model of the single-degree-of-freedom two-rotor system is established using Lagrange’s equation, and a MATLAB/Simulink simulation model is constructed based on the dynamics model. Firstly, a numerical simulation is carried out with completely symmetric system parameters to analyze the Sommerfeld effect of the system. Then, by applying disturbances to the system with different sets of system parameters in the numerical simulation, the self-synchronization phenomenon under different system parameters is studied, system stability after disturbance is investigated, and the ability of the system to recover self-synchronization is evaluated. Finally, the self-synchronization phenomena appearing in the simulation were classified, and how the system parameters will affect the system’s synchronization recovery capability is also given. The results of numerical simulation and analysis show that, with different system parameters, the self-synchronization phenomena can be classified into three categories: stable self-synchronization with in-phase synchronization in the near-resonant region and anti-phase synchronization in the far resonant region, as well as unstable self-synchronization with randomness response after being disturbance when working in the violent resonance region of the system. The result also shows the system’s self-synchronization capability is strongest when the rotor is operated in the near-resonance region of the system. The results of this study can provide a reference for the study of self-synchronization phenomena in more complex vibration systems.