This paper has discussed composition characteristics and variation tendency of carbon and oxygen isotopes from carbonates in Dengying Formation. The δ13C values of the carbonates are between -2.11‰ and 2.71‰, andnegative anomalies are existent at the top and the bottom whereas the main part is relatively stable, with an insignificant decreasing tendency. The δ18O values are between -3.52‰ and -8.76‰, being relatively stable on the whole with a slight decreasing tendency from bottom to top. The composition characteristics and variation tendency are similar to those of the strata of the corresponding period in the world and hence have worldwide correlation significance. The variations of the isotopic content show that the sea level got lowered for a short span at the early stage of Dengying period and then became steady. At the end of Dengying period, the ocean environment in Jiangshan changed intensely, similar to things of the global paleoenvironment in the corresponding period.