The work aims to reduce residual stress of Q345 HAZ. The residual stresses of the HAZ symmetrical position on both weld sides were assumed to be consistent, then residual stresses were measured in blind-hole method for verification. HAZ on one side of weld was subject to shock treatment using ultrasonic impact machine with different technological parameters, then residual stresses on both sides were measured and compared. Removal rate was used to evaluate elimination effect. Difference between residual stresses on both sides of weld fell within 7.5% of maximum principal stress. Surface tensile stress of HAZ could be transformed into compressive stress by UIT, removal rate was 88%~130%. When impact time was unvarying, as removal rate of impact current increased, but the trend became slower. When impact current was unvarying, impact time had slight effects on removal rate. The stresses in HAZ symmetrical position on both sides of weld can be deemed to be equal. Impact current increase can bring about UIT impact increase, leading to further plastic deformation and dislocation motion on HAZ surface, and further improve removal rate of residual stress. Work hardening slowed down the increase trend of removal rate. UIT impact is unvarying when current is unvarying, increasing impact time don‘t affect removal rate significantly.