<p>Aquatic macrophytes constitute a crucial foundation for sustaining the diversity of lake ecosystems. In particular, the carbon isotopes of their cellulose (<i>δ</i>¹³C_cell) represent an essential technical approach for investigating lake carbon cycles and variations in primary productivity. Undertaking research on the distribution characteristics of <i>δ</i>¹³C_cell in aquatic macrophytes and their environmental implications is of considerable significance for comprehending regional lake environmental changes and carbon cycling processes. In this study, Lake Shengjin, a national nature reserve wetland, was selected as the research area. Through integrated field surveys, isotopic analyses, and multivariate statistical modeling (one-way ANOVA, Pearson correlation analysis), this study systematically investigates the <i>δ</i>¹³C_cell distributions in modern aquatic macrophytes and elucidates their environmental drivers. These findings revealed that the <i>δ</i>¹³C_cell of emergent and floating-leaved plants exhibited enrichment with ¹²C, which is indicative of a C3 photosynthetic pathway. In contrast, the <i>δ</i>¹³C_cell of submerged plants displayed enrichment with ¹³C, suggesting the potential involvement of the carbon concentrating mechanisms in their photosynthetic processes. The results of the correlation study indicated that the pH of the water body was the mainly environmental factor influencing the changes in the <i>δ</i>¹³C_cell of aquatic macrophytes in the study area (<i>p</i> &lt; 0.01). This finding was consistent with the results of previous research conducted in the eastern plain lake district and in other regions abroad. This study can offer insights into understanding the distribution characteristics of <i>δ</i>¹³C_cell in aquatic macrophytes of lakes in the middle and lower reaches of the Yangtze River and their environmental implications.</p>