The experiments were carried out on the minute control of monomer composition in acrylic sizes, which were used in manufacturing plant of commercial acrylic sizes. The acrylic sizes were synthesized by solution and emulsion polymerization, and the effects of composition change were investigated. With the control in composition of acrylic monomer, it was possible that acrylic sizes could be synthesized with available physical properties within the Tg range of 15$^{circ}C$. As the mole fraction of ethylacrylate monomer increased, swelling property of acrylic size films increased, but the pick-up property of the size was not changed. From viscoelasticity measurements, it was estimated that the rheological property stability of the solution-polymerized sizes was more better than the emulsion-polymerized sizes at higher temperature sizing process. As size pick-up increased, the physical properties of the sized yarn were improved and the process availability of composition-controlled acrylic sizes was sufficient.