The invention relates to a solid medium heat storage system. The solid medium heat storage system comprises a hot solid medium tank, a cold solid medium tank, at least one hot solid medium heat exchanger and one cold solid medium heat exchanger. The heat exchangers use a solid heat storage medium as a heat exchange working medium. An inlet and an outlet of the hot solid medium tank are correspondingly connected with the cold solid medium heat exchanger and the hot solid medium heat exchanger. An inlet and an outlet of the cold solid medium tank are correspondingly connected with the hot solidmedium heat exchanger and the cold solid medium heat exchanger. A regulating valve is arranged between the outlet of the hot solid medium tank and the hot solid medium heat exchanger. A solid medium feeding pump is arranged between the outlet of the cold solid medium tank and the cold solid medium heat exchanger. The invention relates to a heat exchange system of a thermal power plant. The heat exchange system comprises a boiler tail flue, a tail flue heating surface, a superheater, a steam drum, a steam turbine generator set, a feed water pump and a solid medium heat storage system. The steamdrum is connected with the tail flue heating surface and the superheater, and the superheater is connected to the steam turbine generator set and the cold solid medium heat exchanger correspondingly.The steam turbine generator set is connected with the hot solid medium heat exchanger. The solid medium heat storage system and the heat exchange system have the advantages of simple structure, highcomprehensive utilization of energy and the like.