The invention belongs to the field of solar energy, relates to the solar-thermal energy thermal storage technology, and in particular relates to a single tank phase change thermal storage device for solar energy. The single tank phase change thermal storage device is characterized in that a respiration port, a thermal storage medium inlet, a upper cover, a thermal storage medium outlet and a thermal storage medium discharge gate are arranged on the tank body, a polycyclic multilayer heat exchange coil is arranged in the tank body, and the polycyclic multilayer heat exchange coil is connected between a heat-transfer medium outlet pipe arranged on the upper end of the heat exchange coil and a heat-transfer medium inlet pipe arranged on the lower end of the heat exchange coil in parallel, thus forming a heat-transfer medium circulation pipeline; a thermal storage chamber of the tank body, which contains the thermal storage mediums, is enclosed by the inner wall, the upper cover and the thermal storage medium discharge gate; a sealed heat insulation sandwich is composed of the inner wall of the storage tank and the outer wall of the storage tank; and a thermometer is arranged in the tank. The device disclosed by the invention has the advantages that the phase change thermal storage technology is adopted to enable the thermal storage density to be improved greatly, and the thermal storage volume is efficiently reduced on the premise of same thermal storage capacity; and the storage and release processes of the phase change materials heat are carried out in the same device, thus simplifying the structure of thermal storage device efficiently, and reducing the cost.