Abstract: Experiments in laboratory were conducted to test the efficacy of methanol extract of Gelsemium elegans Benth(MGEB), Chloroform extract of Gelsemium elegans Benth(CGEB) and Gelsemine hydrochloride(GH) against the snail Ampullaria giga. The results showed that, MGEB and GH, Especially GH, had satisfactory molluscidal effects against young snail. The snail mortality was 84% in the concentration of 60mg/L in the 24 hours after treatment, and 100% in 48 hours. 100% in concentration of 20mg/L, and 60% in concentration of 5mg/L in 72 hours. LC50 was 13.17mg/L in 24 hours and 4.80mg/L in 72 hours. It showed no much difference while compared to 45% Fetin Acetate WP (LC50 was 6.91mg/L and 2.18mg/L, respectively). But CGEB had lower toxicity to young snails. The snail mortality was only up to 24% in 72 hours. As to the adult snail, MGEB and GH also have better effect than CGEB. The LC50 of MGEB was 221.63mg/L and 82.28mg/L in 24 hours and 72 hours, respectively; the LC50 of GH was 81.74mg/L and 41.99mg/L in 24 hours and 72 hours, respectively. It showed lower toxicity than 45% Fetin Acetate WP (LC50 was 41.58mg/L and 8.36mg/L, respectively).