Abstract: The nature of resistance to the brown planthopper (BPH),Niloparvata lugens(Stal) was studied in 12 rice varieties.The results indicated that 9 highly resistant varieties exhibited strong nonpreference and antibiosis,as demonstrated by the fact that the insects caged on the tested varieties had few numbers for shelter,high mortality,slow development,less honeydew excreted,and more feeding marks on the leaf sheath.In two moderately resistant varieties,'Fubaoai 21' exhibited certain degree of antibiosis and nonpreference,whereas 'Baoxuan 2' had only weak antibiosis.Some effects of environment conditions on resistance in the Sth leaf-stage rice seedlings were also studied.The results showed that the resistance was influenced by the light intensity and nitrogen fertilizer.Generally,the resistance was reduced and the dead speed of seedlings was accelerated with the decrease of light intensity and the increase of nitrogen fertilizer.A mutual cross-reaction relationship between light intensity and nitrogen fertilizer for resistance was demonstrated.The expression of nonpreference affected by light intensity exhibited different levels in various varieties.