The invention provides a tubular joint of a welding bulb capsule. The tubular joint comprises a supporting rod, an intermediate switchover piece and a main rod, wherein the cross section which is perpendicular to the axle wire direction of the intermediate switchover piece is in a circular-ring shape; the supporting rod is welded on the outer circumferential surface of the intermediate switchoverpiece; the main rod is welded on the end face of the intermediate switchover piece along the lengthwise direction of the intermediate switchover piece, the outer diameter of the main rod is smaller than the outer diameter of the intermediate switchover piece, and the outer diameter of the supporting rod is not larger than the outer diameter of the main rod. According to the tubular joint of the welding bulb capsule, the intermediate switchover piece is provided during welding, when welding the supporting rod with the same diameter, the outer diameter of the intermediate switchover piece is larger than the outer diameter of the main rod, the welding area can be increased, the compact arrangement of the supporting rods is avoided, the hidden welding joint is reduced, the welding quality is improved.