Abstract: The variation of vibrating damping during vibratory stress relief(VSR) is the fundamental of the vibration response changing.The structural damping(or hysteretic damping) during VSR was discussed.The amplitude-dependent internal friction(ADIF) of small laser beam welded samples were measured using dynamic mechanical analyzer.The experimental results show that the structural damping(or ADIF) first increase,then decreases slightly during VSR.This is one of the reasons that result in the variation of vibration response curves.Two methods to evaluate the effectiveness of VSR by vibration response curves were compared according to the VSR code of JB/T5926-1991 and JB/T 10375-2002.The VSR response curves of HT-7U Tokamak welded structures were analyzed.The results indicate that it is practical to adopt the Chinese VSR CODE JB/T 10375-2002 to evaluate the effectiveness of welded stresture VSR.