Abstract: The dynamic transparent-opaque transition behavior of the stimuli-chromic materials makes themselves have the ability to modulate the sunlight, which can reduce the energy consumption of the building. However, these materials usually involved some weak points such as high manufacturing costs, complex operation, and additional power consumption. Herein, a low-cost composite gel (KCA/PNIPAM) with excellent solar modulation ability and high stability was prepared by dispersing poly(N-isopropylacrylamide) (PNIPAM) gel microspheres into a carrageenan (KCA) matrix. In this hydrogel. KCA has a porous 3D network structure, which can effectively support PNIPAM particles, realizing the uniform dispersion and inhibiting the agglomeration and sedimentation of PNIPAM. KCA/PNIPAM gel exhibits the excellent solar modulation ability (ΔT=86%, difference in transmittance at different temperatures), when exposed to xenon lamp and sunlight, KCA/PNIPAM smart windows can lower the temperature by 5°C and 4°C respectively compared with ordinary glass windows. In conclusion, KCA/PNIPAM has the advantages of low response temperature (31.7°C), excellent solar modulation ability, long-term stability, low cost and simple manufacturing, making it a potential candidate for energy-saving materials of building.