Degradable polymers have proven effective for marine antibiofouling. It is important to improve their performance by optimizing their structures. We have prepared polyurethane with degradable polyester segments in the main chain and hydrolyzable poly(triisopropylsilyl acrylate) (PTSA) side chains and used it as the carrier of organic antifoulant (DCOIT). Our study demonstrates that the degradation rate of the polymer increases as the ester group density in the main chain or the length of side chain increases. On the other hand, the release rate of the organic antifoulant increases with the length of side chain. However, it shows a maximum as the ester group density increases. Marine field tests demonstrate that the antifouling of the system increases as the ester group density or the length of side chain increases.