The invention provides a preparation method for aluminum silicon carbide and aluminum silicon carbide obtained with the method. The preparation method for aluminum silicon carbide comprises powder filling and aluminization, wherein in the powder filling step, a groove of an aluminum substrate is filled with powder and a powder plate is formed; an aluminum foil with the depth being 0.5 mm is laid on the surface of the powder plate; other additives except aluminum and silicon carbide are not added into aluminum silicon carbide. According to the preparation method for aluminum silicon carbide, the aluminum foil with the depth of 0.5 mm is laid on the surface of the silicon carbide powder and then aluminization is carried out, so that scouring of molten aluminum to a silicon carbide layer in an aluminization process can be prevented and an aluminum silicon carbide material obtained after the aluminization step is guaranteed to be uniform in internal structure. Moreover, the method provided by the invention keeps the bending resistance of the aluminum silicon carbide material under a condition that no additive is added, so that the thermal conductivity of the obtained aluminum silicon carbide material is increased to 250-280 W/mK.