Abstract: In order to find molluscicidal active components from Nerium indicum leaves on golden apple snail (GAS),Pomacea canaliculata (Lamarck),the lethal and inhibition effect of ethanol crude extracts and component Ⅰfrom N.indicum leaves against different-day old GAS was conducted by the snail-immersed method.The results showed that the LC50 value of component Ⅰ against GAS of 10,30 and 50 days old were 2.86,5.87 and 8.68 mg/L on 6 h after treatment,respectively; and were 0.98,2.31 and 3.16 mg/L on 24 h,respectively.Treated with 2 mg/L of component I for 24 h,the mortality of 10 d-old GAS reached 100%.When treated with 100 mg/L ethanol crude extracts for 72 h,the mortality of 10 d-old and 30 d-old GAS all reached 100%;and the mortality of 50 d-old GAS also reached 100% when treated with 200 mg/L extract for 120 h.Both ethanol crude extract and component Ⅰhad no inhibitory effect on activities of GAS,but promoted upward climbing of GAS.