The invention discloses environment-friendly soldering paste and a preparing method thereof. The environment-friendly soldering paste is composed of, by weight percent, 90% of soldering powder and 10% of flux paste. The soldering powder is composed of, by weight percent, 2% of silver, 0.5% of copper and 97.5% of tin. The flux paste is composed of, by weight percent, 10% of an organic acid activating agent, 20% of an organic solvent, 5% of polyethylene glycol 2000, 2% of paraffin, 4% of hydrogenated castor oil, 4% of a surface active agent, 5% of a corrosion inhibitor and 50% of modified rosin. The preparing method of the environment-friendly soldering paste includes preparing of the soldering powder and preparing of the flux paste; and then the soldering powder and the flux paste are sufficiently mixed to obtain the environment-friendly soldering paste. The soldering powder of the environment-friendly soldering paste does not contain lead, the flux paste does not contain halogen, environment friendliness is better facilitated, residues are few after welding, cleaning is not needed, the spreadability of welding flux is good, a copper mirror cannot be pierced after the prepared soldering paste is welded, and the requirement for packaging high-end precise electronic products can be met.