The invention discloses a method for preventing coal gas from being coked during preheating, which comprises the following steps of: mixing the coal gas with water vapor to form mixed gas and then preheating the mixed gas in a preheater, wherein the preheating temperature is 300-1200 DEG C. The method has the beneficial effects that as the water vapor is adopted as a raw material, the cost is low, and the process is simple and is easy to control; no stopping processing is required, so that the continuous preheating operation of the coal gas can be realized; and when the method is adopted for preheating the coal gas, the number of days generated by continuously using deposited carbon in a pipeline of the preheater is greatly prolonged, the effect of preventing coking or carbon deposition during preheating of coal gas is remarkable, and the production is stable.