Abstract: In order to improve the welding efficiency and quality of Q390 low-alloy high-strength structural steel, double wire welding technology is proposed for Q390 thick plate. The results showed that after multi-layer and multi pass double wire welding, the mechanical properties of the Q390 thick steel plate welded joint were excellent, with higher hardness than the base metal, and the hardness of the bottom welding was higher than that of the filling welding and the top welding. The average tensile strength reached 531.7 MPa, and the average elongation rate could reach 21.2%. The welding residual stress in the weld area is relatively high, with maximum residual stresses perpendicular and parallel to the weld direction reaching 377MPa and 351MPa, respectively. Although both do not exceed the yield strength of Q390 base metal, it is still recommended to adopt appropriate treatment methods for thick plate double wire welds to reduce post weld residual stress.