在无限短转子－轴承的基础上，考虑基础在垂直方向的变形，通过分析油膜力，建立了转子－轴承－基础非线性动力学模型。当基础的刚度下降至一定值时，系统中存在内共振情形，结合现代非线性动力学理论和数值方法，研究了系统在临界点附近的复杂动力学行为。指出：当转速为２６７５ｒ／ｍｉｎ时，基础中会存在低幅值的调幅运动；当转速为３０００ｒ／ｍｉｎ时，基础中会存在高幅值的调幅运动，它远远超过了机组的允许振动幅值。本文的结果表明：基础的刚度与转子刚度之间产生内共振是机组出现异常振动的原因之一，在设计中应该避免这种情况 Based on the infinite short rotor-bearing, considering the deformation of foundation in the vertical direction, the rotor-bearing-foundation nonlinear dynamic model was established by analyzing the oil film force. When the basic stiffness decreases to a certain value, there is an internal resonance in the system. Combined with modern nonlinear dynamics theory and numerical method, the complex dynamic behavior of the system near the critical point is studied. It is pointed out that when the rotational speed is 2675r / min, there will be a low amplitude amplitude modulation movement in the foundation. When the rotational speed is 3000r / min, there will be a high amplitude amplitude modulation movement in the foundation, which far exceeds the allowable vibration amplitude value. The results of this paper show that the internal resonance between the basic stiffness and the rotor stiffness is one of the causes of the abnormal vibration of the unit, which should be avoided in the design