In the study, we examine the influence of welding speed on bead appearance and low-temperature impact toughness of 440 MPa grade high-strength marine steel when laser-arc welding was used. Susceptibility to root humping increases with welding speed, and severe boot humping occurs at welding speed of 1.8 m/min. At the scanning speed of 1.2 m/min, the weld metal exhibits exceptional low-temperature impact toughness. At the low welding speed of 0.8-1.0 m/min, -40 ℃ sharp impact absorbed energy of the weld metal is low, owing to a lot of porosity in the weld metal. When the welding speed increases from 1.2 to 1.8 m/min, the number of acicular ferrite decreases while the amount of lath bainite increases, resulting in a steady decrease in the impact toughness.