The discrete element method (DEM) is employed to study the convection cells of glass beads in a two-dimensional vibrated granular bed. The flow pattern and velocity vectors are consistent with the former experimental results. The solid fractions and the granular temperatures are studied with different vibration acceleration and vibration velocity. A power-law relation exists between the convection flow rate and the dimensionless vibration velocity. The mass flow rate was found to increase with the bed velocity in a power-law relation, J proportional to V-b(2.3), and decrease with the bed velocity in a power-law relation, J proportional to V-b(-0.4), with a fixed vibration acceleration.