I860, 1870 floods occurred during the relatively cold periods in the upper Yangtze River basin. This phenomenon is adverse to the idea that “greater occurrence possibility of floods happened to warmer periods after comparison between cold periods of 19th century and warmer periods of 20th century”. Researches on historical climatic changes during past 500 years in Yunnan, Guizhou and Sichuan, during middle and late 19th centmy and early 20th century, the upper Yangtze River basin is dominated by south-west monsoon. On the 100-year scale, 1860, 1870 floods occurred to the third cold periods during the Little Ice Age. As for the temporal and spatial distribution,the west parts of China is in relatively warm periods during the eastern ports of China is in cold periods (the relatively warm periods before the third cold periods).Relatively warmer and stronger south-west monsoon during around 19th century offered the good climatic background for these two flood events.