The immigrates dominantly of brown planthopper, Nilaparvata lugens Stal in single cropping season in Taihu Lake region is July 10-25, with only one migrating peak. When the immigration occurred during mid and late tillering stages of rice, the insect reached the most serious generation after reproduced only one generation. However, when the immigration occurred in early tillering stage, two generations were needed prior to outbreak. The reproduction from the immigration peak to brachypterous-adult peak was unimportant for the formation of the most serious generation; however, the reproduction following the brachypterous-adult peak had great contribution. As considering rice developmental stage, the reproduction from late tillering stage to the end of heading stage was crucial for the outbreak in later stages. The high temperature in summer could not suppress this insect evidently. The major occurrence time was delayed from mid and late August to September 25-30 due to the changes in rice culturing practices, with the immigration being small while population increase being high. Based on these situations, we suggest that the insect in single-season rice should be controlled dominantly from jointing to the end of booting stages, and if necessary, additionally at heading stage.