The invention discloses a method for purifying, energy saving and ventilating and a purification energy-saving ventilator, and particularly relates to a heat storage type heat exchanger which is used for ventilating indoors and outdoors for a building, and simultaneously purifying fresh air and recovering exhaust energy. The method is characterized in that heat exchange material in the heat exchanger is firmly fixed in a shell of the heat exchanger, and an air distribution mechanism is used for leading two paths of air to alternately pass through different parts of the heat exchange material of the heat exchanger in opposite directions; the heat exchange material is common air filtering cotton, and can exchange heat with air and prevent solid particles in the air from passing through when air passes through the heat exchange material, therefore the air can be purified during ventilation and exhaust energy recovery, and the functions of air disinfection and sterilization, humidification, temperature reduction and the like can be realized. The invention has the advantages of high heat exchange efficiency, simple and compact structure, small volume, low manufacturing cost and long service life, has multiple functions of energy recovery, air purification, humidification and temperature reduction, and provides an economic, efficient and easily popularized multifunctional fresh air ventilator for saving energy, ventilating and purifying air for commercial and household air conditioning rooms.