P(diacetone acrylamide-co-vinylamine) (P(DAAM-co-VAm)) was obtained from the hydrolization of P(diacetone acrylamide-co-N-vinylformamide) (P(DAAM-co-NVF)) which was synthesized by solution free radical polymerization of diacetone acrylamide (DAAM) and N-vinylformamide (NVF), using ammonium persulfate and sodium hydrogen sulfite as initiator. Fourier transform infrared spectrometer (FTIR), nuclear magnetic resonance spectroscopy (1H-NMR), gel permeation chromatography (GPC) and thermal gravimetry (TG) have applied to character the structure, composition and molecular weight of the resultant polymers. The phase transition behavior of the resultant P(DAAM-co-NVF) and P(DAAM-co-VAm) was evaluated by UV-Vis spectroscopy and differential scanning calorimeter (DCS). Experimental results showed that LCST of P(DAAM-co-NVF) and P(DAAM-co-VAm) solutions could be controlled by changing the composition of the polymer and concentration of the solution. Moreover, LCST of P(DAAM-co-VAm) solution could be tuned by bubbling CO2 into the system. LCST of P(DAAM-co-VAm) solution has reversible response to CO2 and N2 switching.