The dynamics and population characteristics of C. medinalis for each generation in the rice growing region of northern Guangdong Province were studied through systematic investigation and female ovarian dissection during 2010 and 2011, and the annual population dynamics were analyzed in combination with data from daily field surveys conducted between 1961-1976 and the recent years after 2000. The results were as follows: 1) with six generations per year in Shaoguan City, C. medinalis had two main density peaks which occurred in early and middle June on earlyseason doublecropping  paddy field, and in late August and early September on lateseason doublecropping  paddy field; 2) the population characteristics of C. medinalis for each generation were determined; 3) the date of moth density peak between 1961-1976 and 2000-2011 had no significant difference, but since 2000, mean daily amount of C. medinalis was significantly higher than that in peak days of early rice from 1961 to 1976 in Qujiang District, Guangdong Province; 4) the occurrence frequency of the highest moth density peak in earlyseason doublecropping  paddy field was higher than that in lateseason doublecropping  paddy field between 2000 and 2011 in Qujiang District, Guangdong Province. The 3rd generation and 6th generation were the major injurious generation of early rice and late rice respectively, whereas the 2nd generation and 7th generation might broke out in special years. Therefore, the enormous increase of the spring immigrants of C. medinalis was the key factor behind the successive outbreak and serious damage in northern Guangdong Province after 2003, while autumn return migration was influenced by the natural environment and human prevention in the rice growing area of northern China, and there were no relationships between the spring immigrants and the autumn return immigrants of C. medinalis.