This paper proposes a novel solar collector/storage system using erythritol as phase change material (PCM). The expanded graphite (EG) in mass fraction of 3% was added into the PCM to form a composite PCM, so as to enhance the thermal conductivity of the PCM. An experimental investigation was carried out to study the performance of the solar collector/storage system in charging process. Then, based on the enthalpy-porosity and melting/solidification models, a numerical model was established and experimentally validated. Furthermore, the heat transfer characteristics in the solar collector/storage system was simulated. Finally, the heat discharging performance of the system was predicted under different inlet temperatures and inlet flow velocities. The results show that the solar collector/storage system with composite PCM has good thermal storage performance, and the daily average storage efficiency reached 39.98%. Meanwhile, when the daily irradiance is larger than 15.23 MJ/m(2), the system could completely finish the latent heat charging process.