At present, the thermocouple bushing used in the production process of aluminium casting, such as insulation furnace, is mostly made of tubular silicon carbide material. Its thermal expansion coefficient is high and thermal stability is poor, which easily leads to bushing explosion and short service life. Moreover, the thermocouple is easily dislocated due to structural defects, resulting in inaccurate temperature measurement and control. 。 In the structure of the product, one end of the sleeve is fitted with a clamp and the other end is fitted with a positioning sleeve. A fixed tube is inserted in the sleeve chamber to make the thermocouple fixed and positioned accurately, eliminate the gap between the thermocouple and the sleeve, prevent the heat release from the furnace body, and solve the problem of inaccurate temperature measurement caused by the translocation of the thermocouple. In terms of material and manufacturing technology, high-quality high-nitrogen composite ceramic thermocouple bushing has been developed by using high-performance ceramic structure preparation technology and phase transformation toughening mechanism. It has the advantages of accurate temperature control data, good thermal stability, non-explosion and long service life.