The cement materials were prepared by self-prepared poly N-isopropylacrylamide (PNIPAM) thermosensitive gel, and the sulfate solution attack test was carried out to measure the mass and strength changes of specimens. In addition, SEM, MIP and hydration heat test were used to study the effect mechanism of PNIPAM gel on the sulfate attack resistance of cement materials. The results show that PNIPAM gel phase transition can release water, promote the hydration of cement materials, improve the internal pore structure, and enhance the mechanical properties of cement materials. 1.0% (mass fraction) PNIPAM gel can reduce the mass loss and strength loss of cement materials subjected to sulfate attack. The PNIPAM gel can counteract the internal damage caused by some expansive erosion products and improve the sulfate attack resistance of cement materials due to its phase transformation characteristics.