The effects of gravity convection perpendicular to growing surface on dendritic morphology growth of model alloy SCN-5% ethanol have been observed by a self-developed experimental apparatus, which has a growth room and an observation system. The results indicate that, compared with those in condition of the absence of gravity convection, the primary arm spacing can be increased and tip radius can be reduced with the increase of growth speed. Gravity convection can result in the rapid growth and more development of the second arm spacing at facing-flow side. The down-stream alternation of dendritic tip growth is attributed to the co-action of the Stokes force and gravity in the flow field.