The purpose of this study is to investigate the plastic deformation behavior of a round bar at the roll-gap during the rolling process of a three-roll planetary mill. The analysis is carried out with the aid of a finite element program MARC adopting the large deformation - large strain theory and the updated lagrangian formulation (ULF). A mesh rezoning procedure is also adopted to improve the uncontrollable running error of elements turning inside out. The mesh system of the whole bar billet is created by using three-dimensional brick elements, and the three-dimensional elastic-plastic finite element model in MARC is chosen to perform the simulations of three-roll planetary rolling processes. The simulation examples consist of three groups. Firstly, three different friction coefficients are adopted to investigate the rolling process. Secondly, totally five different offset angles are used during the simulation of the rolling process. Finally, five different profiles of the roller are used to study the simulation of the rolling process. The successfully obtained numerical results, including equivalent von-Mises stress and plastic strain distributions, rolling force, rolling moment, billet speeds at the entrance and exit planes of the roll-gap are useful in designing the pass schedules of the three-roll planetary rolling processes.