In order to investigate the controllability of $T_{g}$ in acrylic size within the industry-acceptable range, we synthesized acrylic copolymers of designed composition from ethyl acrylate (EA), methyl methacrylate (MMA) and acrylic acid (AA). Relationship between monomer feed ratio and composition ratio of EA/MMA in acrylic copolymers was confirmed by NMR analysis. The composition of MMA in acrylic copolymer was more abundant than in the monomer feed, and it was confirmed that MMA is much more reactive than EA from the evaluation of monomer reactivity ratios. Also, the reactivity ratio of each monomer was very similar in both polymerization method. The emulsion-polymerized size has a higher degree of polymerization than the solution-polymerized size, and the $T_{g}$ of size film increases with molecular weight at a fixed composition. The physical properties such as size pick-up, tenacity and cohesive property of the yarns sized with the acrylic size designed in this study are good, so it is suggested that the developed copolymer is suitable for practical use as warp size.