The invention provides a radioactive source fixing support for radiographic inspection of a large tube-shaped weld workpiece. The radioactive source fixing support is characterized by comprising two support units with the same structure; each support unit comprises a longitudinal arm and a transverse arm; one end of the longitudinal arm is vertical to the centerline of the transverse arm and is fixedly connected with the transverse arm, and the other end of the longitudinal arm and two ends of the transverse arm are provided with coaxial sleeves which are vertical to the longitudinal and transverse arms; in the two support units, a sleeve at one end of one transverse arm and a sleeve at the other end of the other transverse arm are sleeved with the same tube to form a rotary joint, an included angle is formed between the longitudinal arms, and the sleeves of the two longitudinal arms are sleeved with the same tube so as to form the support; and the tube in the sleeves of the longitudinal arms is used for accommodating a source guide tube of a radioactive source probe so as to fix the radioactive source probe. The support is simple in structure, convenient to use, and widely applied to large tube-shaped weld workpieces with different inner diameters.