The invention discloses a thermocline heat-storage peak-regulation system based on a low-pressure heating loop, and a peak regulation method. The peak-regulation system comprises a heat storage moduleand a peak regulation module, wherein the peak regulation module comprises a throttling valve, a bypass throttling valve, a first fused salt pump, a second fused salt pump, a first fused salt valve,a second fused salt valve, a first steam valve and a second steam valve; and the peak regulation method comprises the step that an acting state of a turbine is changed by the peak regulation module according to an input peak regulation target, namely dynamic peak regulation is realized. The system and the method disclosed by the invention have the beneficial effects that efficiency of a thermal power generating unit for increasing and reducing loads can be increased; flexibility and economic efficiency of the unit can be increased; the structure is simple; and operations are convenient.