To solve the problem of the shortened cycle life of phase-change latent heat storage due to the large subcooling degree and serious phase stratification of mirabilite phase-change materials, a graphene oxide/mirabilite composite phase-change material (GO-MCPCM) was prepared with Na2SO4·10H2O-Na2CO3·10H2O-NaCl phase-change composite as a matrix and graphene oxide (GO) as additives. The microstructure and properties of GO and GO-MCPCMs were characterized by scanning electron microscopy, transmission electron microscopy Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetry-Differential scanning calorimetry, respectively. The results show that the O/C ratio in oxidized graphene oxide is increased by 65.75%, the structural defect level is increased from 0.224 to 1.088, indicating that the oxidation-treated graphene has no agglomeration phenomenon and has good hydrophilicity and compatibility. The crystalline phase transition temperature of GO-MCPCMs is 23 ℃, the degree of subcooling reduces to 0 ℃, only sodium sulfate decahydrate releases heat, and the crystalline hydrate is Na2SO4·10H2O with a grain length of approximately 2 cm. The maximum latent heat of GO-MCPCMs crystallization at a mass fraction of 0.075% is 156.7 J/g, and the attenuation rate of the latent heat of GO-MCPCMs crystallization at a mass fraction of 0.075% is 4.3% after 500 solid-liquid cycles. Therefore, the addition of GO can improve the thermal stability of the mirabilite composite phase-change material, and graphene oxide/mirabilite composite phase-change material prepared has a good thermal cycle stability and a long service life.