Abstract: On the basis of heat transfer function, the mathematical model of thermal conductivity inversion by full-field temperature information is deduced, and the feasibility of thermal conductivity inversion during welding is proved.Infrared thermography and thermocouple were combined to measure the welding temperature field during a fixed-point tungsten inert-gas arc welding on a LY2 piece.By full-field temperature information, the variation curves of thermal conductivity with temperature during heating and cooling were obtained.The results show that thermal conductivity values during welding are different with those under stable condition, and the temperature variation direction has a distinct effect on thermal conductivity, viz.thermal conductivity shows delay phenomenon during welding.