The invention discloses a smelting method for producing Φ12-25mm HRB500E straight steel bar by microalloying. The chemical composition of the steel bar is: C: 0.19-0.25%, Si: 0.60-0.80%, Mn: 1.10-1.4%, S: ≤0.04%, P: ≤0.04%, N: 0.01~0.015%, Ti: 0.03~0.05%, V: 0.05~0.07%, Cr: 0.1~0.3%, the sum of the mass percentages of Cr+Mn≤1.55% , Ceq≤0.54%; smelting method: add pre-deoxidation composite slag lotion to the converter tapping, the mass percentage composition of the slag lotion is: 5‑10% fluorite, 65‑75% calcium carbide, 15‑25% limestone; converter Add pre-deoxidation composite slag lotion after tapping, and then add silicon-manganese alloy, ferrosilicon, and high-carbon ferrochromium alloy in sequence. All alloys must be added at 1 / 3 of tapping, and all alloys should be added at 3 / 4 of tapping. Finished, the high nitrogen composite strengthener is added after the addition of the converter alloy, the addition amount is 0.6-0.8kg / t, and its composition: N 12-20%, Ti 18-25%, after the titanium-iron and vanadium-nitrogen alloys are added Carry out soft blowing, the soft blowing effect can be as large as 100-200mm in diameter of exposed molten steel after breaking the steel slag.