Poly (N-isopropylacrylamide-co-methyl methacrylate.) (P(NIPA-co-MMA)) hydrogel was synthesized by making use of the phase separation technique in the mixed solvent (distilled water/glacial acetic acid). This hydrogel responds to external temperature changes very quickly owing to its macroporous network structure formed during the copolymerization/crosslinking process. In this paper, the on-off switch behavior of the P (NIPA-co-MMA) hydrogel with different content of hydrophobic component (MMA) was further investigated and proved to be more sensitive. This fast responsive hydrogel with hydrophobic component and improved sensitivity of its on-off switch behavior would have potential applications in the field of drug-controlled release.