Abstract: A sintered flux for submerged arc welding of grade 800 MPa high strength steel was developed. Using the flux and the corresponding welding wire, the submerged arc welding was conducted on Q690E high strength steel plate. The welding performance of the flux and the microstructure and mechanical properties of the welded joint were studied. The results show that after welding with the flux and the corresponding welding wire, the slag detachability of the weld seam was good, and no adhesive slags and pressing pits existed. The interface between weld seam and base metal was smooth. The microstructure of the weld seam consisted of granular bainite, and the content of harmful elements and H₂O met the standard requirements. The mechanical properties of the joint were excellent, with the tensile strength of 760-900 MPa, the yield strength of no less than 690 MPa, the elongation of no less than 15%, and the impact energy at -40℃ of no less than 47 J. The tested value of diffusible hydrogen content in deposited metal was lower than 4.0 mL/100 g. Both the mechanical properties and the diffusible hydrogen content met the standard requirements.