A series of thermosensitive hydrogels were prepared from the various molar ratios of N-isopropylacrylamide, zwitterionic monomer, N,N＇-dimethyl (acrylamidopropyl) ammonium propane sulfonate (DMAAPS), and N,N＇-methylene-bis-acrylamide. The influence of the amount of DMAAPS in the copolymeric gels on the swelling behaviors in water, various saline solutions, and various temperatures was investigated. Results indicated that the higher the DMAAPS content in the hydrogel system, the higher the swelling ratio and the gel transition temperature. In the saline solution results showed that, when the salt concentration was greater than the minimum salt concentration (MSC) of poly(DMAAPS), the deswelling behavior of the N-isopropylacrylamide gel was suppressed more effectively when more DMAAPS was added into the copolymeric gels; but the swelling ratios of the present copolymeric gels did not significantly change while the salt concentration was lower than the MSC of poly(DMAAPS). In addition, only the sample containing 12 mol % DMAAPS (D4) exhibited an antipolyelectrolyte＇s swelling behavior when the salt concentration was greater than the MSC of poly(DMAAPS). In other words, only when the amount of DMAAPS added into the gel is over some proportion, can the hydrogel show an antipolyelectrolyte＇s swelling behavior in concentrated salt solution. In saline solutions, the anion effects were greater than the cation effects in the presence of common anion (Cl-) with different cations and common cation (K+) with different cations for these gels. Finally, the more DMAAPS content in the hydrogel, the higher the diffusion coefficient in dynamic swelling.