The invention relates to the field of energy utilization, and discloses an energy storage and power generation system and a control method thereof. The energy storage and power generation system comprises a concentrated ammonia water storage tank, a generator, a separator, a condenser, a liquid ammonia storage tank, a turbine expander, an evaporator and an absorber, and further comprises a pressurization branch and a dilute ammonia branch, wherein the concentrated ammonia water storage tank, the generator, the separator, the condenser, the liquid ammonia storage tank, the turbine expander, theevaporator and the absorber are sequentially connected to form a circulation loop, the turbine expander, the evaporator and the absorber are arranged in a turbine generator set, the condenser communicates with a first outlet in the upper part of the separator, the generator is connected to a low grade heat source, one end of the pressurization branch is connected with the bottom of the liquid ammonia storage tank, the other end of the pressurization branch communicates with the top of the liquid ammonia storage tank, the two ends of the dilute ammonia branch are connected to the separator andthe absorber, and the dilute ammonia branch communicates with a second outlet in the lower part of the separator. According to the energy storage and power generation system, energy storage, power generation and refrigeration can be realized by utilizing the low grade heat energy.