The invention discloses a 
narrow gap weld seam temperature measuring device and a 
narrow gap weld seam temperature measuring method. The device comprises a 
heat conducting block, a support compression spring, a temperature measuring element, and a 
temperature recording instrument, wherein the 
heat conducting block is arranged on the top of the support compression spring; an insulating layer is arranged between the 
heat conducting block and the support compression spring; and the temperature measuring element is connected with the heat conducting block and the 
temperature recording instrument respectively. The method comprises the following steps of: (1) cleaning the temperature measuring device, and 
polishing the heat conducting block which is contacted with a workpiece until red 
copper metal color appears; (2) cleaning the temperature measuring element to make a working end have no oxidation layer; (3) connecting the temperature measuring element with the heat conducting block; (4) placing the temperature measuring device into a temperature measuring point of the 
weld seam, and tightly adhering the free surface of the heat conducting block to the surface of the workpiece; (5) 
coupling the temperature measuring element with the 
temperature recording instrument; (6) heating the workpiece, measuring temperature and recording a temperature value; and (7) taking the temperature measuring device out of the weld seam of the workpiece, and cleaning and saving the temperature measuring device. The 
narrow gap weld seam temperature measuring device has the advantages of simple structure, easy 
assembly and disassembly, and accurate and real-time 
temperature measurement, no damage to the weld seam area, and guarantee of the cleanness of the weld seam area.