A solid-gas thermochemical resorption heat transformer cycle was proposed for the integrated energy storage and energy upgrade of lowgrade thermal energy in this paper. The working characteristic of the proposed cycle was analyzed theoretically and the performance of the energy storage system was investigated experimentally using a sorption working pair MnCl2-NaBr-NH3. The research results show that the thermal energy can be stored in the form of chemical potential resulting from the reversible thermochemical resorption processes of the working pair. The integrated energy storage and energy upgrade of low-grade thermal energy is achieved simultaneously by performing the presented solidgas thermochemical resorption heat transformer. The advanced thermochemical resorption energy storage technology can provide an effective method for the high-efficient utilization of lowgrade thermal energy. The thermal energy can be effectively upgraded according to the heating demand of external users at different working temperatures. For example, at a heat input temperature of 128 °C during the energy storage phase using a sorption working pair MnCl2-NaBr-NH3, the heat output temperature can reach 140 °C and 144 °C after energy upgrade during the energy supply phase. The corresponding thermal energy storage efficiency is 0.21 and 0.11, and the exergy efficiency is 0.25 and 0.13, respectively. Moreover, the energy storage efficiency decreases with the increase of the temperature lift of low-grade thermal energy.