The invention discloses a method for prolonging the service life of a coal gas plate-type preheater, and belongs to the technical field of hot blast heaters. The method for prolonging the service life of the coal gas plate-type preheater comprises the following steps that the lowest coal gas preheating temperature of the plate-type preheater is limited to be higher than or equal to 130 DEG C, and the lowest temperature of a smoke outlet pipe of the plate-type preheater is limited to be higher than or equal 130 DEG C. By means of the method for prolonging the service life of the coal gas plate-type preheater, the service life of the coal gas plate-type preheater can be prolonged, and cost is saved.