The invention relates to a device used for energy storage heating, sterilizing and PM2.5 reducing through off-peak power and used for a small-sized apartment. A unique three-chamber combination module is adopted, and the device comprises an equipment shell, a first-stage draught fan, a balancing chamber, a second-stage draught fan, a wind distributing passageway, a front normal-temperature wind passageway, a rear normal-temperature wind passageway, a left normal-temperature wind passageway, a right normal-temperature wind passageway, a left rising pre-heating chamber, a right rising pre-heating chamber, a falling heat storage chamber, an electric heating chamber, an electric heating element, an acid fire-resistant material heat storage body, an alkaline fire-resistant material heat storage body, a long heat-resistant steel bar, a short heat-resistant steel bar, a phase-change heat storage body, a left heat-resistant steel partition plate, a right heat-resistant steel partition plate, a device bottom plate, a heat storage box bottom plate, a wind distributing passageway bottom plate, a wind distributing passageway front side plate, a wind distributing passageway rear side plate, a device top plate, a heat storage box top plate, a warm wind passageway, a warn wind spraying guiding plate, an intelligent-control power supply box, various heat-resistant steel partition plates and the like. According to the device used for energy storage heating, sterilizing and PM2.5 reducing through the off-peak power and used for the small-sized apartment, heating can be achieved all day long by using the off-peak power, the functions of high-temperature burning, high-temperature adsorbing combination, transverse heat transmission and waste heat recovering are further achieved, indoor air can be thoroughly purified without cost, secondary pollution is not generated, and the device is suitable for indoor energy storage heating and air purifying in winter.