The invention provides a preparation method of a light heat insulation brick. The method comprises the following steps of: taking materials according to a formula, adding a proper amount of water, stirring, aging, extruding and forming to obtain a first green brick; drying the first green brick for the first time at normal temperature to obtain a second green brick; drying the second green brick for the second time to obtain a third green brick, and drying the third green brick for the third time to obtain a fourth green brick; then naturally cooling to normal temperature to obtain a fifth green brick; carrying out programed temperature rising on the fifth green brick for calcining for the first time and then carrying out programmed cooling to obtain the heat insulation brick; carrying outheat preservation treatment on the heat insulation brick and cooling to normal temperature to obtain the light heat insulation brick; the formula comprises 10-35 parts of corundum, 20-55 parts of mullite, 0.5-1 part of polystyrene balls, 0.4-0.8 part of coke powder, 1-3 parts of silicon oxide, 1-3 parts of titanium dioxide, 3-5 parts of calcium oxide, 3-5 parts of yttrium oxide, 1-3 parts of magnesium oxide and 1-3 parts of epoxy resin. The preparation method has the advantages of simple process, and stable product performance and long service life.