The experiments of single crystals growth for vitamin C were carried out on growth rates of different orientations (［010］

［001］and ［100］).Under various temperatures and supersaturations

the directional growth rates were measured. The kinetic parameters were regressed by the least-square method and verified by significance test. In aqueous and ethanol aqueous solution

the kinetic parameters changed greatly

and the controlling step of growth differed from each other. So crystals in aqueous solution are often in rod form

while always in plate form in water-ethanol.The effects of solvent on directional growth were analyzed according to steric effect of solvent molecules and hydrogen bond interaction at solution-crystal interface.