The invention relates to a low-temperature, halogen-free, low-solid-content modified rosin-type welding flux. The welding flux is prepared form, by mass, 10-15% of modified rosin, 1-5% of organic acidactivator, 0.35-1% of glycerin, 0.009-1% of benzotriazole, 0.3-1 % of triethanolamine, a surfactant and the balance organic solvent, wherein the surfactant is 0.5-3% of the mass of the organic acid activator. The prepared low-temperature, halogen-free and low-solid-content modified rosin-type welding flux prepared has good fluidity, no precipitation and delamination phenomena, no halogen elements, a small amount of modified rosin, a good spreading rate, good weldability, bright and full welding spots and less residues after welding, little corrosion is caused, and cleaning is not needed; therequirements for environmental protection are met; an operation method is sample, the temperature is moderate, there are less experimental steps, the cost is low, less by-products are generated in a synthesis process and are easy to remove, and the synthesis time is short.