Abstract: Through testing 45 carbonate samples collected from Permo-Carboniferous caol measures of the Hedong coalfield,the distributions characteristics of carbon and oxygen isotopes in sequences are analyzed,whose feasibilities for sequence subdivision and correlation,as well as for study of relative sea level variations and late Paleozoic facies are also discussed.It is shown that the distributions of carbon and oxygen isotopes in sequences(third order)are different between C₂ and P₁¹.In sequences of C₂ the values of BX δ¹³C and δ¹⁸O varied gradually heavier from TST to HST;in sequences of P₁¹,however,the values of δ¹³C varied lighter from TST to HST,but the values of ¹⁸O heavier,both of which presented rhythmicity vertically.Laterally the values of δ¹³C and Z generally present an increasing trend southwards.The distribution of carbon and oxygen isotopes in sequences are controlled by many factors,such as coal accumulation,terrigenous supply,;paleoclimate,depositional environment and geologic time.