Abstract: Insecticidal activities on buds and flowers of Solanum tuberosum were not reported at home and abroad. Study on insecticidal activities and action ways of extracts from dry buds on dark condition and flowers of S. tuberosum against Mythimna separate can provide clue and theoretical basis for formulating new type of botanical insecticide. The thesis conducted insecticidal activity of ethyl acetate extracts from dry buds on dark condition and flowers of S. tuberosum (Zhuangshu 3) by immersion and sandwich methods. The results showed that ethyl acetate extracts from dry buds and flowers had very strong contact toxicity against 5th instar larva of M. separate, the corrected mortality were 52.0% and 61.36%, respectively when the extracts were diluted 5 times. The extracts had very strong developmental inhibition action against the 3rd instar larva, developmental inhibition rates of 1, 2, 3, 4, 5 and 6 d after treatment were 100% and 100%, 76.92% and 61.54%, 66.67% and 59.26%, 70.27% and 45.95%, 72.55% and 49.02%, 67.12% and 35.62%, respectively. The extracts had very strong anaesthesia action against the larva, anaesthesia rate were 68.0% and 66.0% in one hour, regression equation were Y=2.0542+3.1331X and Y=3.0114+2.3334X, RT₅₀ were 8.71 and 7.12 h. The extracts had very strong contact toxicity against larvae of Plutella xylostella, Pieris rapae, Artogeia brassicae and Pontia daplidice, corrected mortality were 75.0% and 58.33%, 87.50% and 95.0%, 100% and 93.33%, 100% and 100% (diluted 5 times, 4 times to P. xylostella ), respectively. The extracts also had very strong contact toxicity against Lipaphis erysimi with corrected mortality of 98.52% and 97.79% (diluted 30 times).