The invention discloses a chemical vapor deposition process. The process comprises the steps that the set pressure of a reaction cavity when the CVD reaction is carried out is determined; an exhaust valve arranged on a gas discharge pipeline is opened to a first angle, wherein the first angle is 10%-90% of a second opening angle of the exhaust valve when the CVD process is carried out; a reactiongas is introduced into the CVD reaction cavity until and the pressure of the reaction cavity reaches the set pressure; the opening angle of the exhaust valve is adjusted to the second angle, and the gas pressure in the reaction cavity can be kept at the set pressure through the angle; and the CVD process is carried out. According to the process, the problem of reacted secondary product rechargingat the gas discharge pipe orifice is effectively solved.