In this work, a phase change material based photo-thermal cells was prepared and the solar light triggered thermal storage charging and discharging property was investigated. The graphene nanosheet was uniformly dispersed into paraffin to form phase change materials based photo-thermal cells. The thermal conductivity, enthalpy, heat capacity, optical absorptive property and photo-thermal performance of photo-thermal cells were investigated. The results show that adding 50 ppm of graphene nanosheet in the phase change materials could largely improve the optical absorptive property in visible range and thermal storage capacity charging rate. To calculate the effective thermal storage capacity of phase change material, the results show that the phase change material based photo-thermal cells has larger effective thermal storage capacity than water, indicating the phase change material based photo-thermal cells is promising in solar thermal utilization systems.