The structures of the aqueous solutions of sodium formate and lithium formate are studied according to the growth conditions of the crystals under different supersaturations and temperatures by Raman spectroscopy. The effects of temperature, concentration, supersaturation and cation on the structures of solutions and the structure difference between lithium formate solution and lithium formate monohydrate crystal are analyzed. The result shows that the concentration, temperature and supersaturation effect the structures of the solutions slightly and the cation effects the frequency of the bands greatly.