In order to study the modulation effect of large-scale background field on the relationship between ENSO and Indian summer monsoon precipitation, and to better predict the interannual variation of Indian summer monsoon precipitation under the climate warming background, this paper studies the relationship between ENSO and Indian summer monsoon precipitation in the past 500 years based on ten sets of reconstructed ENSO indices and Indian precipitation data, the reasons for its existence and how to understand this phenomenon.This paper mainly focuses on the influence of ENSO on Indian summer monsoon.Results show that, firstly, the relationship between ENSO and Indian summer monsoon precipitation is not immutable in the past 500 years (1470-1999), generally shows a negative correlation.The negative correlation is weak during Little Ice Age (LIA) and strengthened during Current Warm Period (CWP), but begins to weaken after the 1980s.Secondly, the relationship between Indian summer monsoon precipitation anomaly and ENSO in the past 500 years is certain, not random.Thirdly, the relationship between the Indian summer monsoon precipitation anomaly and the amplitude and cycle of Niño indices are very different during LIA and CWP.The amplitude and cycle of ENSO during CWP are significantly larger than those during LIA, which leads to a stronger negative correlation between Indian summer monsoon and ENSO during CWP.But the average states of the two periods are almost same.