The invention discloses a determining device and a measuring method thereof for residual heat storage quantity of a phase change energy storage material. The determining device and the measuring method belong to the technical field of phase change material state evaluation. The determining device comprises a thermal insulation box, wherein a heating device, a heat exchange circulating water pipeline, a water inlet temperature measuring device, a water outlet temperature measuring device and a phase change energy storage material temperature measuring device are arranged inside the thermal insulation box, the water inlet temperature measuring device is arranged at a water inlet of the internal heat exchange circulating water pipeline inside the thermal insulation box, the water outlet temperature measuring device is arranged at a water outlet of the internal heat exchange circulating water pipeline inside the thermal insulation box, the phase change energy storage material temperature measuring device is used for measuring temperature of a phase change energy storage material to be measured, and the heating device is used for heating the phase change energy storage material to be measured; a power consumption measuring device is arranged for recording power consumption of the heating device; an outer surface temperature measuring device is arranged on the outer surface of the thermal insulation box, and is used for measuring heat dissipating quantity of the thermal insulation box; and an external waterway communicated with the heat exchange circulating water pipeline is arranged outside the thermal insulation box, and a flow meter is arranged inside the external waterway. The determining device and the measuring method thereof can obtain the residual heat storage quantity of the phase change energy storage material through measurement and calculation in real time.