To better understand the heat-transfer character and flow of liquid gallium,a natural convection flow of liquid gallium was numerically simulated by using single phase method on the heat transfer of liquid gallium in a two dimensional enclosure. The effects of boundary condition and Grashof number on the flow and the convective heat transfer behavior are investigated. The numerical results which include temperature and velocity graph are compared with the experimental data and reasonable agreement is achieved. In a case that thermal conductivity takes a leading part,when Grashof number goes up,convection will gradually play a more important role.