The invention provides a preparing method of a foamed aluminum sandwich plate and belongs to the field of porous metal materials. Core aluminum alloy (material A) is fused, preserved and tackified at a temperature T1, and a foaming agent TiH2 treated by pre-oxidation is added into the tackified core aluminum alloy melt (material A), stirred and dispersed; a foaming die is preheated to the temperature T1, an aluminum or aluminum alloy plate (material B) is preheated to a temperature T2 which is 10-15 DEG C lower than the solidus temperature of the aluminum or aluminum alloy plate (material B), and the difference between T1 and T2 is 10-20 DEG C; the preheated aluminum or aluminum alloy plate (material B) is padded at the bottom of the die, the tackified core aluminum alloy melt (the material A) containing the TiH2 is poured into the die, and the temperature of the die is controlled at the T1 to carry out heat preservation and foaming; and after the foaming process is finished and cooling is carried out, the foamed aluminum sandwich plate of which the surface layer and a foamed aluminum core are metallurgically combined is obtained, and the thickness of the surface layer of the sandwich plate is controlled through the thickness of a panel.