Abstract: Welding experiments of butt joint and T joint of Q690 D thick plate for construction machinery were performed with D-Arc welding technology. Formation of weld, microstructure and microhardness of welding samples were analyzed. And the mechanical properties of tensile test, bending test and impact test were also carried out. The results showed that, compared with conventional gas shielded welding, butt joint with 25 mm thickness plate and T joint with 30 mm thickness plate by D-Arc welding technology could reduce the weld by more than one third.The depth of fusion obviously increased, and formation of weld was good. The microstructure of D-Arc joint with large current parameter was not exceptionally coarsened. The maximum hardness in heat-affected zone and the minimum hardness of softening zone were not outliers compared with the base metal hardness. The tensile test, bending test and impact test were qualified.