The invention discloses halogen-free high-activity low-splatter solder wire soldering flux and a preparing method thereof. The halogen-free high-activity low-splatter solder wire soldering flux comprises, by mass, 2-10 percent of alcohol or alcohol ether high-boiling-point solvent, 0.08-1.5 percent of high-activity iodate, 2-10 percent of compound binary organic acid, 0.5-5 percent of halogen-free activity enhancer, 2-15 percent of viscosity modifier, 0.04-0.2 percent of efficient surface active agent and the balance modified rosin and rosin derivatives. The preparing method includes the steps that the compound rosin and the viscosity modifier are added into a container to be heated and stirred until the compound rosin and the viscosity modifier are completely melted down, the organic acid, the novel high-activity iodate, the efficient surface active agent and the high-boiling-point solvent are added to be stirred continuously, and therefore the soldering flux is prepared. The prepared halogen-free soldering flux for solder wires is free of halogen compounds, tin is easy to apply in the soldering process, splatter is little, smells are light, soldering spots are bright and full, damage to the health and the environment is avoided, and the post-soldering reliability effect of an electronic product is ensured.