We present new high-resolution carbonate carbon isotope data (δ13Ccarb) from four sections in the Yangtze Platform, South China, ranging in age from Tremadocian to early Katian. The data have five distinct characteristics: 1) A prominent δ13Ccarb increase from −2.79‰ to 0.13‰ at the base of the Ordovician within the Tremadocian Cordylodus angulatus-Rossodus manitouensis Zone. 2) A positive δ13Ccarb excursion from −2.56‰ to 0.58‰ in the Paltodus deltifer Zone during the late Tremadocian. 3) A gradual increase in δ13Ccarb from −1.16‰ at the top of the Oepikodus communis Zone to a peak of ~0.74‰ in the Baltoniodus triangularis Zone at the Floian-Dapingian boundary. 4) A moderate rise in δ13Ccarb from 0.59‰ to 1.24‰ in the middle Darriwilian Dzikodus tablepointensis Zone. 5) A distinct positive δ13Ccarb excursion from 0.86‰ to 2.32‰ at the base of the Amorphognathus superbus-Hamarodus europaeus Zone during the early Katian. These excursions can be correlated with C-isotopic trends identified in age-equivalent successions in South China, Argentine Precordillera, North America, and Central Sweden, demonstrating their potential for global correlations and providing a composite, high-resolution chemostratigraphic framework for sedimentary records of the Lower-Upper Ordovician in South China. Besides, our data demonstrate a temporal coincidence between the long-term rise in δ13Ccarb and the Great Ordovician Biodiversification Event, suggesting that enhanced organic matter burial and accompanied climatic cooling and oxygenation may have played an important role in promoting the increases in biodiversity during the Ordovician. •High-resolution δ13C stratigraphy for nearly the entire Ordovician from South China.•Five distinct positive δ13C excursions that can be correlated globally are revealed.•Data suggest climatic cooling and oxygenation may have facilitated the GOBE.