The extraordinary cold caused by heavy snow is one of the important signs of clamatic change in historical periods. Professor Zhu Kezhen is the founder of this stuty. According to Xu Xiake's Travels this paper has revised Prof.Zhu's conclusion about the beginning of the extraordinary cold caused by heavy show in China and the range of climatic change and arrived at the following conclusions: 1. The cold period of 17th century in China came more than half a centary earlier than in 1651.2. The range of temperature chang in 17th century is much wider than in Zhu's conclusion.