Abstract: The original deposits of the carbonate rocks from the Wumishan Formation in Lingyuan,western Liaoning are explored on the basis of carbon and oxygen isotopic and Mn/Sr ratios.The δ¹³C_PDB values range between-2‰ and 2‰ and δ¹⁸O values range between-10‰ and-4‰,with an average of 0.15‰ and-6.2‰,respectively.The δ¹³C values exhibit a markedly positive shift in the carbonate rocks from the upper and middle parts of the first member of the Wumishan Formation.This shift may be caused by abundant algal production and organic carbon increase.The climatic cooling down and glaciation gave rise to the increase of δ¹⁸O values,especially in the levels with negative δ¹³C values.The carbon and oxygen isotopic evolution in the carbonate rocks may be correlated to the sea-level changes.