Abstract: It is known that the actual temperature-rise data of steel tube in the heat treatment furnace are the necessary parameters for preparing proper heat treatment process. With conventional measuring devices like thermal couple and infrared pyrometer, etc., the data as measured are so deviated from the actual temperature. Comparatively, the "Black Box" temperature-measuring device is capable of provide the minimum measurement deviation. Application of the measurement technique of the said heat-resistant "Black Box" to the steel tube continuous heat treatment furnace is described here in the article. Based on the digitalization of the heat treatment process, the application of the "Black Box" temperature measurement technique for improvement and optimization of the heat treatment process is discussed.