Abstract: In order to study the effect of heat conduction mode on the microstructure and properties of 800 MPa class marine high strength steel additive components, 800 MPa class marine high strength steel components were deposited by wire arc additive manufacturing (WAAM) technology under different processes, and microstructure characterization and mechanical properties testing of components were carried out. When deposited along the height direction, the bottom microstructure of the component is mainly acicular ferrite and martensite, the middle and top microstructures are massive and acicular ferrite + granular bainite. The yield strengths in the horizontal and vertical directions are 708 MPa and 652 MPa, the tensile strength are 895 MPa and 831 MPa , and the impact absorbed energy at −60 ℃ is 66 J and 86 J, respectively. When deposited along the transverse direction, the microstructure of the component is fine acicular ferrite and lath martensite, the yield strength and tensile strength reach 929 MPa and 1020 MPa respectively, and the impact absorbed energy at −60 ℃ is 92 J. The results indicate that the mechanical properties of the 800 MPa class marine high strength steel WAAM component are highly sensitive to the heat conduction mode, and optimizing heat conduction process can significantly improve its comprehensive mechanical properties.