The aerobic biodegradability of acrylate copolymers for warp sizing was studied using the shaking-bottle incubating method for their COD removal rates after being cultivated for 30 days. Influences of acrylate unit chemical structure, including the alkyl chain length of the ester group, α-methyl group, and molar content of acrylate units, on the biodegradability of the sizes were investigated. The acrylate copolymers were prepared via free radical copolymerization of acrylates with acrylic acid in ethanol. The biodegradability of acrylate copolymers strongly depended on the structure and molar content of the acrylate units. After being cultivated for 30 days, poly(MA-co-AA) was biodegraded substantially and the COD removal rate exceeded 50%. However, the biodegradability of poly(BMA-co-AA) was poor and the removal rate was 10%.