A computational study has been made for a three dimensional double diffusive convection with molten Pb-Sn by using finite volume method. In this work, two vertical walls have different temperature and different concentration while remaining walls are adiabatic. Buoyancy ratio, which changes between N = -0.1 and -10, is the main governing parameter during work. Other parameters are taken as fixed with Pr = 0.02, Le = 7500 and Ra = 5×10³. It is found that changing of buoyancy parameter becomes more effective on heat transfer than that of mass transfer.