Hydrate salt is an attractive solid-liquid phase change material because of its high energy storage density. However, its applications have been limited owing to the supercooling and phase segregation. In order to solve these problems, we propose to make the silica gel in the saturated solution of sodium sulfate by means of in-situ polymerization. According to our experiments, the latent heat of saturated solution of sodium sulfate in silica gel is about 238.1 J/g and the phase change temperature is 30℃. With some surfactant, it can endure more than five months of heating-cooling cycles stably in subtropical spring and summer. Using scanning electron microscope and Fourier transformation infrared spectroscopy, we found that the microstructure of silica gel was mainly amorphous with some small crystals distributed in it. We believe that adding the silica gel produces a porous structure, which helps the crystal growth of sodium sulfate hydrate and hence, suppresses the supercooling and phase segregation.