The present study made a detailed carbon and oxygen stable isotope analysis on the lacustrine carbonates from the Lower Cretaceous Yixian Formation, Yixian, western Liaoning, NE China. The δ13C values of lacustrine carbonates range from -4.825 to 6.870‰, and the δ18O values range from -16.190 to -7.143‰. Theδ13C and δ18O values indicates that the hydrological characteristics tend to be closed, relatively hot and dry palaeoclimatically resulting a high salinity background caused by volcanic activity.