Abstract: Abstract：Carbon and oxygen isotopes in drill core of Wudaoliang Group have well recorded Early Miocene environment changes and palaeoclimate cycles in northern Tibetan Plateau. The Wudaoliang Group as thick as ~150 m consists mainly of limestone, dolomite limestone and marl, with a discontinuity occurring at the depth of 50.0-51.0 m in the drill core. Carbon and oxygen isotopes change considerably at the depth of 140-145 m, where both maximal δ18O and minimal δ13C occur two times. δ18O and δ13C reach to the minimum at the depth of 140.7 m, corresponding to global cooling Mi-1 recorded by the deep-sea drilling of oceanic deposits at the Miocene/Oligocene boundary. Seven eccentricity cycles of 1.2 Ma are recorded between 140.7 m and 14.2 m in depth, and 9 minor cycles of 17.4 ka are recorded from 69.86 m to 62.60 m in depth. It is further inferred that Early Miocene lake in northern Tibetan Plateau initiated at (24.1±0.6) Ma and ended at (14.5±0.5) Ma according to Palaeo-climate cycles recorded by carbon and oxygen isotope changes of lacustrine deposits, and that annual temperatures changed from 19°C to 21°C (~20°C on average) in Wudaoliang basin in Early Miocene.