Abstract: The microstructure, tensile properties of small diameter and thin-walled 0Cr18Ni9 EH oil pipe welded joints under different pulse TIG welding (P-TIG)processes and fatigue performance of EH tubing joint under the best process were analyzed by using optical microscope (OM), tensile test, fatigue test and scanning electron microscope.The results show that the microstructures of the weld zone of the pipe joints under different processes are all δ-ferrite+austenite, and the austenite grain in the heat-affected zone is obviously coarsened. When the base current is 20 A, the peak current is 50 A, the pulse frequency is 0.5 Hz and the pulse width ratio is 70%, the tensile properties of the small diameter thin-walled pipe joint are the best, and the fatigue strength of the pipe joint is 106.5 MPa. The fatigue fracture contains crack source zone, steady propagation zone and instantaneous fracture zone, as the stress amplitude decreases, the proportion of the instantaneous fatigue zone in the fatigue fracture gradually decreases.