The recently discovered Yangchang deposit in Zhenxiong County, Zhaotong City, Yunnan Province is an ultra-large-scaled buried phosphate deposit. Previous research on this deposit mainly focused on the metallogeny, while the study of sedimentary geochemistry and the paleoenvironment is lacked. More importantly, the inorganic (δ¹³C_carb) and organic (δ¹³C_org) carbon isotopes as well as their relationships in the early Cambrian were rarely reported. In this study, three drill cores (ZK001, ZK0701, ZK1512) in Yangchang phosphate deposit were selected for high-resolution investigations of δ¹³C_carb and δ¹³C_org. Both δ¹³C_carb and δ¹³C_org show negative shifts in the top Precambrian Dengying Formation and the bottom of its overlying Zhujiaqing Formation, which is consistent with the global Basal Cambrian Carbon Isotopic Excursion (BACE), likely due to the oxidation of organic carbon reservoir. However, we did not find significant positive shifts in the overlying strata (i.e., Zhujiaqing Carbon Isotopic Excursion, ZHUCE), which may be caused by sedimentary hiatus given that the Yangchang phosphate deposit is mostly intra-clastic phosphorus-rich deposits. Nevertheless, we propose that this phosphate deposit was mainly formed during the Fortunian according to the comparison between the δ¹³C_carb in the three drill cores and the composite profile of δ¹³C_carb in South China. The comparisons for the δ¹³C_carb and δ¹³C_org values in the drill cores ZK001 and ZK0701, show that the average value of the ΔC_carb-org (difference between δ¹³C_carb and δ¹³C_org) is 28.8‰ and 22.2‰ in the Dengying Formation, and these values change to 31.7‰ and 31.7‰ at the bottom of the Zhujiaqing Formation, and 29.6‰ and 29.8‰, in the middle and upper of the Zhujiaqing Formation, respectively. We propose that the decoupled δ¹³C_carb and δ¹³C_org occurring in the middle of the Zhujiaqing Formation may be caused by the increased primary productivity or buried organic carbon. In summary, the high-resolution paired inorganic and organic carbon isotopes in this work indicate the formation time of Yangchang phosphate deposit and shed light on associated paleoenvironmental changes, which also support the regional stratigraphic correlation.