Cellulose acetate has a high melting temperature due to intense intermolecular hydrogen bonding and is not significantly different from the deterioration temperature, so decomposition may occur during processing. Generally, in order to prevent pyrolysis of CA in the melting process, it is dissolved by using a solvent such as CS2 or H2SO4. However, it is not suitable for extrusion and injection process, and plasticized CA composition is prepared using plasticizer. In general, Dioctyl phthalate (DOP) is the most widely used plasticizer, and polyethylene glycol (PEG), glycerin (GC) triacetin (TA) and the like are partly used as environmentally friendly plasticizers. In this study, lactic acid was used as a compatibilizer and viscosity modifier in addition to plasticizer to prepare a composite. When the content of lactic acid is 5 wt% or more, phase separation occurs, so that the viscosity of the composition is controlled by blending in the range of 1 similar to 5 wt%. The melting characteristics of the prepared compositions were confirmed by DSC and TGA, and specimens were prepared by injection molding. The effect of lactic acid content on the melt viscosity was measured and the yield stress, yield strain and elastic modulus were calculated by the evaluation of tensile properties. The composition of this study showed a viscosity change of about 10 similar to 50% compared with the conventional one and the thermal properties were also different. The thermal properties were also different. In addition, the change of mechanical strength was observed depending on the degree of commercialization of additives.