【Aim】 To investigate the effects of two molluscicides, niclosamide ethanolamine salt and metaldehyde, on the gut microbiota structure of Pomacea canaliculata, and the responses of the gut microbiota. 【Method】 Healthy individuals of P. canaliculata with the body length of 25 mm to 30 mm were treated with niclosamide ethanolamine salt and metaldehyde at LC₂₅ and LC₅₀ and under static starvation conditions for 96 h. The survival rates and the structural changes of gut microbiota were analyzed. Illumina MiSeq high-throughput sequencing of bacterial 16S rRNA V3-V4 region was conducted for 14 gut samples of P. canaliculata. 【Result】 The actual mortality rates of P. canaliculata exposed to metaldehyde at LC₂₅ and LC₅₀ were 9.44% and 12.22%, respectively, higher than theoretical values. The actual mortality rates of P. canaliculata exposed to niclosamide ethanolamine salt at LC₂₅ and LC₅₀ were 3.89%-4.44% lower than the theoretical values. Both molluscicides decreased the gut microbiota diversity. Metaldehyde reduced the species richness by 25.2%-32.0%, which significantly exceeded the reduction (7.8%-15.7%) caused by niclosamide ethanolamine salt. The β-diversity analysis showed minor differences of the gut microbiota structure under niclosamide ethanolamine salt treatment. However, metaldehyde drastically altered the gut microbiota structure, decreasing the relative abundance of Cloacibacterium from 61.49% to 7.78%-11.92% and increasing the relative abundance of Bacteroides to 21.46%-62.21%. Moreober, distinct gut microbiota variations were observed after treatments with metaldehyde at LC₂₅ and LC₅₀. 【Conclusion】 Metaldehyde causes greater disruption to the gut microbiota balance of P. canaliculata than niclosamide ethanolamine salt, especially affecting key genera (Cloacibacterium, Lactococcus, and Bacteroides) involved in the balance. Gender-specific responses to the two molluscicides are observed. Female snails maintain higher levels of beneficial bacteria in the gut and stronger molluscicide tolerance than male snails. Both male and female P. canaliculata may alleviate molluscicide stress by enhancing gut microbiota metabolism or regulating host immune functions.