The paper aims to explore the media flow mode and media flow field characteristics of the horizontal vibratory mass finishing under different vibration parameters. The model was established based on the discrete element method (DEM) to simulate the movement characteristics of the media under the horizontal vibratory mass finishing. The media flow field characteristics and the flow regime change of the media under different parameters were analyzed, the influence of media bed height ratio, change of the empty area and convection area ratio on the convection intensity of the entire particle system and the influence of the average velocity of the media on the flow field was studied, and then simulation results had verified by high-speed photography speed test experiments. Under the external vibration, the media flow field was divided into three areas:convection area, mixed flow area and steady flow area. As the frequency increased, the average velocity of the media reached the maximum at 18 Hz and then decreased. As the amplitude increased, the average velocity of the media increased. The changes in media bed height ratio, the empty area and convection area ratio were consistent with the change trend of the average velocity with the vibration parameters. As the amplitude increases or the frequency reaches about 18 Hz, the average velocity becomes larger, and the media bed gradually changes from the upper layer to the lower layer and from the only solid state,of steady-flow to the liquid state with convection and mixed flow. The average velocity of the media is consistent with the change trend of the convection intensity, so the change of the latter can be predicted by the former. Moreover, increasing the amplitude is more effective than increasing the frequency to improve the fluidization degree of convection.