Abstract: Single fluoride NaF, Na₂SiF₆ and YbF₃ were selected as active fluxes for welding experiment of TC4 titanium alloy, and their weld penetration, weld width and plasma morphology were analyzed by 5 mm single laser welding test. The results showed that the active fluxes selected in the single laser welding test had different effects on weld width and weld penetration, but all of them could reduce weld width and increase weld penetration, among which YbF₃ had the best effect. The electron density of the welding plasma was effectively reduced after active fluxes were applied.