The invention discloses a method for determining silicon dioxide in silicon carbide, belonging to the field of metallurgical chemical industry. The method comprises the following steps of: controlling certain temperature to only dissolve the silicon dioxide in the silicon carbide by hydrofluoric acid, and determining the content of the silicon dioxide in the silicon carbide through a hydrofluoric acid resistant system of an inductively coupled plasma emission spectrometer. With the method, the content of the silicon dioxide in the silicon carbide can be accurately determined, and the determination range of the method can be 0.005%-20%.