Secondary compounds play an important role in crop resistance to pest insects.The extract from resistant variety IR36 was purified by means of diatomite systemic_solvent and combination silica gel chromatography isolation method.A acicular crystal was obtained.Based on some chemical reactions and its character,the compound isolated was identified preliminarly as an indican flavone.The influence of the crystal on survival and grouth of Nilaparvata lugens (Stal) biotype Ⅱ larvae was studied.The results showed that the crystal showed negative influence on survival rate，body-mass increase rate and molting rate of adalts of N. lugens.