Various agronomic traits of crops, particularly in resistance to pathogen, pest and weed, should correlate significantly with crop secondary metabolism and metabolite. We sought, in this instance, to determine the biochemical basis of resistance of rice plants to Nilaparvata lugens. The aerial part of resistant rice plant (IR36) was immersed with 85% ethanol in the room temperature and ethanol-soluble extracts were prepared. Different solvents including petroleum ether, ethyl acetate, absolute ethanol and water were then used to extract the ethanol-soluble extracts and different solvent fractions were obtained. These fractions were tested for effects on mortality of the brown planthopper nymphs. EtOAc fractions had significantly impacts on mortality of brown planthopper nymphs 3 d after treatment, with corrected mortality of 26.0% and 48.0% being recorded for 1st and 2nd instar nymphs at 2000mg/L concentration, and 3rd and 4th instar nymphs at 3000mg/L concentration, respectively. EtOAc fractions of resistant rice plants (IR36) were separated by column chromatography over silica gel and 5, 7, 4’ -trihydroxy-3’ , 5’ -dimethoxyflavone (tricin) was isolated. Artificial diets containing tricin of different concentrations（50～500μg/ml）were prepared to feed on nymphs of the brown planthopper in test-tubes. Twenty 3rd instar nymphs were then introduced into each test-tube for bioassay. After the brown planthopper nymphs fed15 days on diets containing tricin, weight of honeydew of the nymphs reduced as tricin concentrations in the diets increased. The mortality rate of the nymphs increased with increasing tricin concentration. The corrected mortality was 58.21% for the 3rd instar nymphs and 31.75% for 4th instar nymphs respectively at 500μg/ml concentration. However, even though at 500μg/ml concentration the adding weight and development period of 3rd instar nymphs and 4th instar nymphs were no significantly different between treatments. Additionally, tricin (500μg/ml) significantly inhibited oviposition and feeding of the brown planthopper females in choice tests when spread on susceptible rice plant (TN1). Our results suggested that tricin in resistant rice plant played an important role in resistance to brown planthoppers.