A collecting agent for separating gold from auriferous pyrite is prepared by the following raw materials in part by weight: 30-34 parts of xanthate, 12-14 parts of glycerin, 4-7 parts of sodium hexametaphosphate, 18-22 parts of terpenic oil, 10-12 parts of black powder, 2-3 parts of dimer acid, 1-2 parts of phthalic acid ester, 12-14 parts of diltiazem nitrile ester, 2-3 parts of 3-aminopropyltrimethoxysilane, 4-5 parts of nitrilotriacetic acid and 10-12 parts of activating agent. The collecting agent has a collecting function and a foaming function; foams are stable; the collecting ability is high, so that the recycling rate of the gold ores is high, the selectivity is high, and the grade of the gold ore is also high; and moreover, by using the collecting agent, the affinity of gold and iron can be reduced, collection on iron can be restrained, and then the grade of gold is improved. By using the activating agent, the surface hydrophobicity of the gold ore is changed, the internal structure is activated, and the gold collecting performance of the collecting agent is improved.