The swelling behavior for the poly(N-isopropylacrylamide) (NIPAAm) hydrogel prepared in various conditions such as various polymerization media, i.e., deionized water, acetone, and ethanol aqueous solution, and different polymerization temperatures were investigated in this work. The gels were also assessed for suitability in drug-controlled release. The results indicated that the swelling behavior of the gel was dependent on the polymerization media and temperature, that is, the swelling ratios of gel were related to the pore size and the looser or denser structure of the gel. In addition, the pore size of the gel could be controlled by adjusting the surrounding temperature. Hence, the gel can be used to deliver drugs with different sizes.