<p>During long-term use, the connecting spring gradually shifts from linear to nonlinear behavior due to factors like fatigue and wear. This change significantly affects the beam structure's vibration behavior. In practical engineering, the beam structure often faces multi-source excitation caused by power equipment, external environment, and other factors, leading to complex and adverse vibrations. However, few studies have considered the combined influence of multi-source excitation and internal nonlinearity on the beam structure's vibration behavior, limiting the development and practical use of nonlinear vibration control in beam structures. To solve this problem, this study introduces a nonlinear oscillator to form a nonlinear mixed element (NME) with the connecting spring without destroying the original connection structure. Furthermore, a vibration model for a thin beam system under the simultaneous existence of an internal NME and double excitations is offered and established. The thin beam system's nonlinear vibration behavior under the simultaneous existence of an internal NME and double excitations is discussed and analyzed. The results show that the rational use of NME can synchronously and beneficially decrease the thin beam system's vibration response when the excitations have different angular frequencies or phase differences. Therefore, this study contributes to enhancing the value of nonlinear theory in engineering applications and makes the control of nonlinear vibrations in beam structures more aligned with engineering practice.</p>