The spatial distribution of summer rainfall anomalies over eastern China often characterized by meridionally banded structure. The possible change of it in response to global warming is of great significance to water resource management and disaster prevention. Previous studies show critical role of climate variability on modulating these rainfall modes while seldom studies considered model’s internal variability on investigating their responses to increased greenhouse gas. Based on model simulations with different forcings from the fifth Coupled Model Inter-comparison Project (CMIP5), this paper analyzes the response of the leading modes of eastern China summer rainfall to increased CO2 concentration with consideration of model internal variability. The results show that increased CO2 would not change the leading modes of eastern China summer rainfall. The tripole and dipole mode during the recent decades would still be the leading modes in the abrupt quadruple CO2 experiment (4×CO2) and 1% per year increased until quadrupled CO2 experiment (1%CO2) with the dipole mode plays a more dominant role. However, the frequency, intensity and trend of these modes will change. Compared to pre-industrial control simulation (piControl), the temporal variability of the tripole and dipople mode both decrease under 4×CO2 forcing. The variability of dipole mode intensifies while tripole mode weakens under 1%CO2 forcing. With the gradually accumulation of CO2, the occurrence of the positive and negative phase of these modes will change. The phase of tripole mode which featured with drought over the Yangtze River Basin while flood over North and South China would happen more frequently. So does the “Southern flood and northern drought” phase of the dipole mode. Compared to piControl simulation, the sea surface temperature and atmospheric circulation anomalies associated with the dipole and tripole mode both weaken under 4×CO2 forcing. Whereas under 1%CO2 forcing, their differences are regional dependent. The tripole mode is associated with weakened anomalies over the Indian and western North Pacific Ocean while the dipole mode is associated with stronger central and eastern tropical Pacific and North Pacific sea surface temperature anomalies.