The U-Pb isotopic age of Hanshan gabbro in North Qilian Mountains is 347.1±6.4 Ma, belonging to Hercynian. The Hanshan gabbro is located in the south of the deposit and is obviously related to the deposit. Theore-forming age of the deposit is 339±10 Ma, being of Hercynian too. The petrogenic age is earlier than the ore-forming age, possibly suggesting that the rockbody provided heat for the deposit. This conclusion is theoretically important and practically significant in the search for gold deposits in the study area, because there occur a lot of intermediate-acid rocks there.