Abstract: Based on the lubrication principle of rolling process and the mechanical vibration theory, a vertical vibration model of single-stand aluminum cold rolling mills was established with the consideration of dynamic friction state in roll gap to study vertical vibration phenomena in high speed rolling of thin strips. This model includes the geometric model of roll gap, the dynamic friction model of the roll-strip working interface, the distribution model of principle rolling stress and friction stress, and the two-degree-of-freedom vertical structure model which is coupled with the former three models. In order to analyze the vertical vibration mechanism and system stability under dynamic friction state in roll gap, the rolling force curve and normal rolling stress distribution curve were simulated separately on Matlab/Simulink platform for validating this model, with the actual data of a single-stand aluminum cold rolling mill. Moreover, the dependences of the system stability on strip entry thickness, mixed friction state and rolls-strip surface roughness were dis-cussed in this article.