The invention relates to the technical field of welding residual stress relieving, in particular to an intelligent control system for relieving welding residual stress, and further discloses an intelligent control method for relieving the welding residual stresses. The intelligent control system comprises a control end and an execution end. The control end comprises a host computer system, a signal generator and a power amplifier which are sequentially connected. The execution end includes an electromagnetic vibration exciter and an X-ray diffractometer, wherein the X-ray diffractometer is connected with the host computer system, and the upper computer system is used for adjusting high-frequency vibration impact parameters of the electromagnetic vibration exciter through the signal generator and the power amplifier according to a residual stress detection result of the X-ray diffractometer. According to the technical scheme, the residual stress can be relieved by local high-frequency vibration impact, the vibration impact parameters can be determined according to the residual stress level, and the optimal residual stress relieving effect can be achieved.