The invention discloses a sintering method of a silicon carbide preform and a preparation method of an aluminum silicon carbide board. The sintering method comprises the following steps: putting a preform biscuit into a sintering furnace, letting furnace temperature rise from room temperature to 200 DEG C at the speed of 5 DEG C/min, extracting flue gas from the sintering furnace into a combustion chamber, and setting the combustion chamber to big flame; letting furnace temperature rise to 400 DEG C at the speed of 4 DEG C/min, and turning down flame of the combustion chamber; letting furnace temperature rise to 600 DEG C at the speed of 4 DEG C/min, keeping the temperature for 0.5 h, and increasing flame of the combustion chamber; stopping extracting flue gas, sealing a flue gas outlet of the sintering furnace, letting furnace temperature rise to 850 DEG C at the speed of 3 DEG C/min, keeping the temperature for 1h, cooling the furnace body, and opening the furnace door so as to obtain the silicon carbide preform. According to the above sintering method of the silicon carbide preform, flue gas is extracted into the combustion chamber and discharge of paraffin steam is promoted. Thus, generation of carbon black residue on the surface pores of the silicon carbide preform is avoided. Dewaxing time is greatly shortened, and sintering time is shortened.