The hot-dry stages with little rain and high temperature has an important impact on agriculture, water conservancy and human health in the middle and lower reaches of the Yangtze River (MLRYR), but there is still a lack of sufficient understanding of the historical division and long-term change law of the hot-dry stages in this region. Based on the daily temperature and precipitation data of the Meiyu season and summer at five stations along the MLRYR (Shanghai, Nanjing, Wuhu, Jiujiang and Hankou) since 1885, the quantitative standards of less rain and high temperature for the hot-dry stages after the Meiyu end date are determined respectively, and the MLRYR hot-dry stages from 1885 to 2020 are defined; combined the uniform temperature standard and the length of summer hot-dry stage, the intensity index of summer hot-dry stage for the 136 years was determined. For the 136 years, the average length of annual hot-dry stages is 21.6 days (including 16 non hot-dry-stage years and 10 autumn hot-dry years), showing 3-6-years, 36-years and 84-years cycles. Since 1951, 1959-1978 was the main peak period of the length of the hot-dry stage, 1980-1987 was the valley period, and then increased slowly; after 1980s, although the long hot-dry stage >30 days tended to decrease, the 15-30 days and high-intensity hot-dry stages occurred frequently; since 1995, the autumn hot-dry stages have increased significantly and summer has had a delay trend. The longest and strongest summer hot-dry stages in the 136 years occurred in 1934, 1967, 1978 and 2013, and the earliest/latest hot-dry stage occurred in the middle of June/middle and late September. In the past 40 years, the number of days with high temperature (≥ 35.0 ℃) in the summer hot-dry stages has increased significantly, and the incidence of high temperature in the summer hot-dry stages has increased from about 30% in the 1980s to more than 50% in recent years, posing a threat to human health. The characteristics of subtropical circulation in the long (strong) summer hot-dry stages are that the Western Pacific subtropical high stably controls the MLRYR, while in the short (weak) summer hot-dry stages, the Western Pacific subtropical high is mostly east or south, and the autumn hot-dry stages are related to the stable westward extension of the subtropical high. The evolution of high temperature days in the summer hot-dry stages is restricted by dual human activities: it is not only related to the global sea and land warming caused by human activities, but also varies from place to place, that is, it is affected by the evolution of local ecological environment and the increase or decrease of urban heat island effect. On the interdecadal time-scale, the continent-ocean temperature difference in the Indo-Pacific monsoon region is found to have an important modulation effect on the interdecadal variation of the length of the summer hot-dry stages in the MLRYR.