The carbon isotopic composition of CO-2, CO and CH-4 extracted by pyrolysis from spinel lherzolite and black pyroxenolite xenoliths in alkali basalt from Damaping has been measured with GC_MS. The results show that, at heating temperatures from 400 to 1 140℃, the δ 13C of CO-2 and CO is -22‰--27‰, and that of CH-4 -30‰--50‰. The data imply that the magma which was generated in the upper mantle by partial melting in the area has experienced the multistage degassing process, and the δ 13C values represent the carbon isotopic composition of CO-2, CO and CH-4 remaining in it, respectively. The carbon isotopic composition of CO-2, CO and CH-4 extracted by pyrolysis from spinel lherzolite and black pyroxenolite xenoliths in alkali basalt from Damaping has been measured with GC-MS. The results show that at at temperatures from 400 to 1 140 ° C, the δ 13C of CO-2 and CO is -22 ‰ -27 ‰, and that of CH-4 -30 ‰ - 50 ‰. The data imply that the magma which was generated in the upper mantle by partial melting in the area has experienced the multistage degassing process, and the δ 13C values ​​represent the carbon isotopic composition of CO-2, CO and CH-4 remaining in it, respectively.