The Bajiazi gold deposit is one of the important gold deposits in the Jiapigou gold belt located in the northern margin of the North China Craton. Ore bodies occur as veins within the Archaean granite-greenstone belt, are controlled by the NW trending Jiapigou fault, and may be genetically related to Mesozoic syenite porphyry. Eight pyrite samples were selected for Rb-Sr isochron dating to determine the mineralization age of the Bajiazi gold deposit. This study obtained an Rb-Sr isochron age of 218.6±1.5Ma (MSWD=1.4), with an initial Sr isotopic ratio ISr=0.71047δ18OW values of the oreforming fluid vary from 3.2‰ to 5.1‰, and δDWvalues vary from -100.7‰ to -88‰, indicating that the oreforming fluid derived mainly from magmatic fluid mixed with minor metamorphic fluid and meteoric water. δ34S values of metallic sulfides range from -0.2‰ to +7.9‰, with an average of +5.7‰, suggesting that the sulfur came mainly from deep magma. 3He/4He ratio of fluid inclusions in pyrite ranges from 1.05 to 1.20 Ra with an average of 1.13 Ra. The percentage of mantlederived fluid involvement into mineralization ranges from 11.6 % to 13.2 %, with dominant fluid from the earth’s crust. The Bajiazi gold deposit formed in the postcollisional extension setting of the northern margin of the North China Craton in late Triassic.