Abstract: The determination methods for ~3 H and ~(14)C in some biological specimens are studied. After combustion, the OBT(organic bound tritium) in biological sample is converted to HTO. The tritium contents of the water is determined by liquid scintillation counting. Carbon in the sample is converted to CO_2 in an oxygen bomb. The latter is finally converted to benzene via three successive reactions CO_2→Li_2C_2→C_2H_2→C_6H_6. The limit detection is 1.2 Bq/L and 1.0 Bq/kg for tritium and radiocarbon respectively. The results of activity in environmental and biological samples are given, such as milk,leaf, soil,animal etc.