Heat storage system and heat storage method for meeting deep peak regulation requirement of power plant unit

The invention relates to a heat storage system and a heat storage method for meeting the deep peak regulation requirement of a power plant unit. In the prior art, the deep peak regulation requirementof a thermal power unit is limited, and the situation can be effectively solved by utilizing heat storage and heat release of the heat storage system. The heat storage system comprises a high-temperature molten salt storage tank (1), wherein one end of the high-temperature molten salt storage tank is sequentially connected with a high-temperature molten salt pump (6) and a water supply molten saltheat exchanger (3) through a pipeline A (16); the water supply molten salt heat exchanger is connected with a low-temperature flow, temperature and pressure monitoring device (5) through a pipeline B(13); the low-temperature flow, temperature and pressure monitoring device is connected with one end of a low-temperature molten salt storage tank (2) through a pipeline B; and the other end of the low-temperature molten salt