Butt welding of Inconel 690 heat transfer tube is conducted by gas tungsten arc welding（GTAW）. The tube welded joints are tested and analyzed by using the tensile tester,flattening tester and optical microscope. Meanwhile,the ANSYS software is used to carry out the primary stress intensity check of the welded joint when the pressure is lost in the design condition. The results show that the center of the weld is dendritic crystal,and the area near the fusion line is coarse columnar crystal. At room temperature,the average tensile strength and yield strength of the joint are 619 MPa and 292 MPa respectively. At 350 ℃,the average tensile strength and yield strength of the joint are 475 MPa and 206 MPa respectively. The fracture of tensile joint runs through the whole weld structure from the fusion zone, forming plastic fracture. The results of flattening test and reverse flattening test demonstrate that the tube joints are in good condition. Through ANSYS analysis,under the design condition,the allowable stress intensity of the heat transfer tube joint at 350 ℃ is 150 MPa,which can meet the requirements of its primary stress intensity, and the margin is large.