Abstract: Drum system of the horizontal worm screen centrifuge as the vibration source of the whole machine is the key study object of the centrifuge's dynamic load and mechanical vibration.Structural resonance and material une-ven distribution are the main causes of vibration of the drum system.The structural resonance can be avoided by modal analysis for the drum system using finite element method.The geometric model of drum system is founded by UG, then it is partitioned by hypermesh using hex grid meshing method.Contact pair and MPC(multipoint con-straint) algorithm are used to achieve a connection between two components with discontinuous grids.The eigenval-ues of drum system are extracted in ansys based on block lanczos algorithm and the solution offers the first eight nat-ural frequencies and vibration modes of the drum system under both the conditions with and without centrifugal pre-stress.The results demonstrate that the structural resonace will not occur at the rated working speed.The centrifu-gal prestress has an obvious effect on the lower natural frequencies.The conclusions provide the basis for research and design on the transient dynamic response of the whole machine and the structure optimization of drum system.