The invention discloses a novel energy storage brick. The novel energy storage brick is characterized by using magnesium oxide as a main material and is prepared from, by weight, 85-95% of magnesium oxide, 1-10% of calcium oxide, 2-8% of silicon oxide, 0.2-3% of ferrous oxide and 0.2-1.5% of aluminum oxide, and the total component percentage content is 100%. The novel energy storage brick is extremely high in heat resistance and not degraded after the long-term use, the service life can reach 20 years, the thermal conductivity is high, and the low-temperature heat is easily extracted; by using magnesium oxide as the main material, the heat storage performance of the novel energy storage brick is more excellent than that of an energy storage brick prepared from a traditional iron oxide material, the energy storage effect is better, and heat conduction and heat dissipation are more uniform; the novel energy storage brick can be applied in an energy storage type electric heater or a water heater and other devices requiring energy storage, can effectively use peak-valley electricity for heating and storing heat, also makes a great contribution to peak cutting and valley filling for the whole power network, saves energy and improves social overall benefits.