This paper aims to ascertain the impact of the East Asian summer monsoon (EASM) on immigration of rice leaf roller, Cnaphalocrocis medinalis Guenée, in the main rice-growing regions of south China and provide a scientific basis for the medium and short term warning of C. medinalis. The influence of the EASM advancing and retreating on the immigration of C. medinalis in China was analyzed using the pentadly moth catches of C. medinalis from 2000 to 2016 and the daily reanalyzed meteorological dataset from the National Center of Environment Predicting (NCEP) in USA. The results showed as follows:(1) The northward migration of C. medinalis was closely related to the northward advancement of EASM. Except for the immigration beginning dates of C. medinalis in the rice-growing region of South China which was earlier than the beginning dates of the northern margin of EASM, the two beginning dates were basically synchronized in other rice regions. The first appearance and second appearance of the northern margin of EASM in different rice-growing regions had certain indication significance for the beginning of C. medinalis northward immigration. (2) The peak events of northward immigration generally occured in the control areas of EASM. When the north margin of EASM moved to the north of 30°N from mid-June to early August, more peak events of northward immigration usually with large populations took place in the main rice-growing regions of southern China. The duration of EASM north of 30°N was positively correlated with the annual occurrence of C. medinalis. (3) The middle and late ten days in August was the period of monsoon transition in East Asia and was also a period combined the northward migration with southward migration of C. medinalis populations when the first batch of southward migration peaks occurred in southwest China and the north of the rice-growing regions between the Yangtze River and the Huaihe River. From the beginning of September, when EASM began to retreat and the prevailing northeast wind with the attribute of winter monsoon moved southward rapidly, the populations of C. medinalis moved southward simultaneously. (4) In this paper, the atmospheric background for the outbreak of C. medinalis in the rice-growing regions between the Yangtze River and the Huaihe River in 2007 were investigated. Firstly, the strong southwest monsoon from the end of June to July increased significantly the immigrating amount of C. medinalis in the rice-growing region along the valley of Yangtze River which laid a foundation for the large-scale migration of C. medinalis from the rice-growing region along the valley of Yangtze River to the rice-growing region between the Yangtze River and the Huaihe River. Secondly, the anomalous low precipitation in the south of the Yangtze River and South China in July led to the further accumulation of hygrophilous C. medinalis populations in the rice-growing region along the valley of the Yangtze River and the rice-growing region between the Yangtze River and the Huaihe River. Thirdly, the delaying of EASM retreating in August and the relative warm of the North China and the region between the Yangtze River and the Huaihe River in September detained C. medinalis populations in these areas. At last, the beginning dates and the peak dates of their migration southward were unusually late.