The invention relates to the field of austenitic stainless steel material welding, in particular to an SA-213TP347HFG steel small diameter tube welding method.The method comprises the following steps: 1, conducting treatment before welding, wherein a V-shaped groove is machined out of an SA-213TP347HFG steel small diameter tube to be welded, the single-side groove angle is 33-38 degrees, and grinding treatment is conducted on the groove; 2, controlling the welding environment, wherein the temperature is higher than or equal to 0 DEG C, the air speed is less than or equal to 2 m/s, and the relative humidity is less than or equal to 75%; 3, welding the tube to be welded through manual tungsten inert gas arc welding (TIG), wherein an TIG welding machine with high frequency arc striking and current attenuation is selected, the electric arm length in the welding process is 1-2.5 mm, an ERNiCr-3 welding wire is selected, the welding root is filled with argon and coated with an anti-oxidation protective agent for protection, the argon purity is 99.99%,and the flow rate is 8-15 L/min, narrow weld bead and short bead intermittent welding is adopted, tracking is conducted from time to time for temperature measurement so that the welding interlayer temperature cannot be higher than 70 DEG C, weld lines on each layer are covered with cloth dipped in purified water for cooling, and in the welding process, a slope with length being 7-9 mm is formed through grinding at a joint between each weld line and the previous weld line.