It is controversial where the hydrocarbon in Kokyar Condensate Field derived from. Correlating the characteristics of biomarkers from the Tertiary condensate oil with the possible source rocks, the result indicates that the condensate gas mainly originates from Permian hydrocarbon source rock due to existing 3-methylsterane, relatively high abundance of diahopane and unknown C30-terpane but no 4-methylsterane in the condensate oil. The natural gas in the field is wet gas for the abundance of heavy hydrocarbon is high and the carbon isotope values of ethane are heavy. Both of argon isotope and maturation indicate that the gas did not come from a single source. It is pointed out that the gas originates mostly from Carboniferous-Permian rock and partly from the Jurassic rock. Thus, the condensate and gas in Kokyar Field derive respectively from different source for carbon isotope values of ethane in gas are obviously heavier than those in whole condensate oil.