Carbon isotope of gastropod shell carbonates in lakes is directly correlated with dissolved inorganic carbon (DIC) in lake water, providing vital signals for the regional carbon cycle in lakes. Lakes are widely distributed in the central Yunnan region, and little is known about the DIC characteristics of these lakes. Anularya mansuyi shells are a unique genus of the lakes in central Yunnan Province. Here, two living Anularya mansuyi shells (QLH-A and QLH-B) were collected from Lake Qilu and their carbon isotope composition of shell carbonate (δ¹³C_shell), longitudinally along their growth span were studied to reveal possible dissolved inorganic carbon shifts in Lake Qilu's waters. Results showed that: (1) The δ¹³C_shell values could be used to identify the two Anularya mansuyi shells' growth in the mother's internal environment, the average values of δ¹³C_shell were -3.78‰ and -5.55‰, with ranges of variation of 2.07‰ and 3.03‰, respectively. In lake water environment, the average δ¹³C_shell values of the two shells were -2.90‰ and -3.28‰, with ranges of variation of 1.81‰ and 1.74‰, respectively. (2) During the period when Anularya mansuyi grows in the lake water, the δ¹³C_shell recorded the δ¹³C_DIC characteristics of lake water DIC, indicating that the DIC of the Lake Qilu water body was mainly affected by atmospheric exchange and the biological system. The δ¹³C_DIC values of DIC showed no significant seasonal variation in Lake Qilu. (3) Followed algal bloom, the organic matter decomposition caused by the death of aquatic algae in lake system would lead to negative δ¹³C_DIC. Basing δ¹³C_DIC records of 2012-2013, the negative δ¹³C_shell during the second half of 2013 was consistent with the Yunnan Drought Event in 2013 and revealed the δ¹³C_shell of the Anularya mansuyi had the potential to record significant changes in the lake ecosystem. The fossil shells of Anularya mansuyi are widely distributed around lakes in central Yunnan, and these fossil shells can be used as potential documents to identify the DIC characteristics of water bodies and changes in lake ecosystems during geological historical periods.