Vibration and force fluctuation in hot rolling mills hurts the stand equipments. The most pervious studies have been mentioned self-excited vibrations will not occur in hot rolling mills. Forced vibrations are the most important problems in hot rolling mills. This kind of vibration degrades product quality, and sometimes damages the mill. So Vibration observed in hot rolling mills against cold rolling is not of style self-excited because in hot rolling process due to high temperature elasticity module of strip reduces considerably. On the other hand dependency of yield stress to temperature and strain rate can affect on stability. In order to control and suppress these vibrations in hot rolling operations, a comprehensive understanding of the dynamic nature of plastic deformation of the strip and vibration in the mill are required. In this project, a new approach to modelling hot rolling process has been proposed. Additionally a simulation in Simulink of Matlab software has been provided to modelling hot strip rolling and forced vibrations due to various defects on the bearing of work rolls, gears in main gear, ovality existence in work rolls and backup rolls and misalignment in gear couplings. at first chapter different style of vibrations of hot rolling mill stand is considered. Second chapter is talking about the most important structure models of mill stand. At third chapter previous studies about rolling process model are mentioned and a new model for hot rolling process is provided. Fourth chapter is about different defects in some components of structure. In this chapter external forces due to these defects are modelled. Results of this simulation in fifth chapter exhibit effect of these defects on force fluctuations and mill vibrations.