In order to solve the problem of vertical vibration of 1850 four-roll aluminum strip cold rolling mill in a large enterprise， the vibration characteristics of rolling mill system in time domain and frequency domain are studied according to the dynamic characteristics of the rolling mill under different working conditions by combining field vibration test with dynamic simulation， and the influence of different rolling process parameters on the dynamic characteristics of rolling mill is analyzed. Based on the six-degree-of-freedom dynamic model of the four-roll aluminum strip cold rolling mill system， the rolling force fluctuation model， interfacial friction process and work roll motion model constitute the multifactor coupling model with interface constraints. At the same time， the simulation analysis is carried out on the inherent characteristics of the rolling mill， the main vibration mode and the sensitivity of the main vibration mode. The results show that the self-excited vibration occurs in the rolling mill system， the core vibration frequency of the working roll is 290 Hz， the vibration frequency of the vibration center is 250~350 Hz， and the vibration source is in the roll gap， rolling speed， tension of strip， friction state of roll-gap and thickness of strip are the important factors that affect the coupling of rolling interface. The vibration of supporting roller and frame in this frequency band is the result of system interaction.