Abstract: The ethanol extract of the aerial part of Sida rhombifolia L.was extracted with petroleum ether and ethyl acetate to give the petroleum ether extract,ethyl acetate extract and water phase.Toxic activity of the ethanol extract and three crude extracts against the 4th-instars larva of Aedes albopictus Skuse and Ampullaria gigas Spix was tested.It showed that the ethanol extract and ethyl acetate extract had obvious insecticidal activity against the 4th-instars larva of A.albopictus ,while petroleum ether extract and the ethanol extract showed higher molluscicidal activity against A.gigas .Eleven known compounds were isolated from the ethyl acetate extract through further phytochemical investigation,their structures were identified as m -hydroxybenzoic acid(1),glyceroyl monopalmitate(2),syringic acid(3),gallic acid(4), β -sitosterol(5),stigmasterol(6),scopoletin(7),kaempferol(8),5-hydroxy-7,4'-dimethoxyflavanone(9),tiliroside(10) and β -sitosterol-3- O -glucoside(11),respectively,by 1H NMR and 13C NMR.Compound 2 exhibited potent insecticidal activity against the 4th-instars larva of A.albopictus ,with LC50 value of 28.66 μg/mL and 13.50 μg/mL after treatment in 24 h and 48 h,respectively.