The effects of gravity and kinetic undercooling upon the melt/crystal interface in a vertical Bridgman-Stockbarger crystal growth system by numerical simulation. Thermal transport, melt convection and kinetic undercooling are simulated by two-dimensional transient calculations. Time evolution of the centerline interface location difference is tracked. This study then compares and discusses the results among the different gravitational acceleration. We also investigate the effects of the undercooling on the interface.