The invention discloses a preparation method of a silicon carbide coating by a chemical vapor deposition (CVD) method. The preparation method of the silicon carbide coating by the CVD method comprisesthe following steps that (1) a heating box of a deposition furnace is started to enable the temperature up to 100-160 DEG C; (2) graphite matrix is placed on a rotary plate in the deposition furnaceto drive the graphite matrix to rotate; (3) the deposition furnace is subjected to vacuum-pumping, then is subjected to argon filling, and the vacuum-pumping and the argon filling are repeated for many times; (4) a furnace cavity heating system is started to heat the deposition furnace and the deposition furnace is subjected to vacuum-pumping at the same time, after the deposition temperature is reached, the temperature is held for a certain period of time, and argon is filled in the deposition furnace, so that the pressure in the furnace can reach 40-60 K pa, and then vacuum-pumping is carried out; (5) hydrogen, argon and alkanes are fed into the heating box and then liquid chlorosilane is fed into the heating box , and then mixed gases with the chlorosilane are fed into the deposition furnace; and (6) after deposition, the transportation of the hydrogen, the chlorosilane and the alkanes are stopped, the transportation of the argon gas is maintained, the deposition furnace is flushedand cooled, then the deposition furnace is inflated, a furnace body is opened, and a graphite work piece with the silicon carbide coating is removed.