The dissolution of untreated cellulose filter paper was performed in formic acid/dichloromethane/sulfuric acid of ternary solvent mixture. This solvent system showed a good solubility to cellulose at most compositions examined. The ratio of 76/4(f)mimic acid/sulfuric acid in v/v) was considered as an optimum concentration in consideration of the degree of substitution(DS) and intrinsic viscosity(IV). As the temperature of dissolution increased from 15$^{circ}C$ to 35$^{circ}C$, IV of the cellulose formate decreased from 1.67 to 1.00, while the DS of cellulose formate was independent of the dissolving temperature. The solubility of the cellulose formate depended on the IV and DS values. Particularly, the solubility of cellulose in dimethyl sulfoxide or in dimethyl farmamide was poor no matter what the values of IV and DS. Cellulose flrmate of DS 1.76 was almost regenerated to cellulose by hot-water treatment in 4 hours.