Abstract: The Nansi Lake, which lies along the Grand Canal and in the southwest part of Shandong Province, is the name for the four lakes as: Zhaoyang Lake, Nanyang Lake, Dushan Lake and Weishan Lake. Based on the study of the historical records, this paper describes the evolution processes of the Nansi Lake and analyzes the historical background for the changes. It points out that the four lakes all underwent different evolution process. Among them Zhaoyang Lake came out first. At the beginning of the Ming Dynasty (1368-1644A. D.) it was one of the important watersupply places for its western canal in Shandong Province. However, with the canal route being changed to its east in order to avoid the intrusion of the Huanghe River flood in 1567A. D., Zhaoyang Lake’s function changed. It became an accommodation for both the Huanghe River flood and the superfluous water of the canal. From 1723 A. D. Zhaoyang Lake also received the sand from the canal for the safety of the dyke of the canal. With the increasing muddy sediments of the Huanghe River flood and the expansion of the inning area in its basin, also without its primary water resources, Zhaoyang Lake became smaller and smaller. After the canal route had changed, an artificial tank for protecting the canal from the attack of its eastern hilly riptide was needed. Dushang Lake was born for this purpose. Dushang Lake had another name as Nanyang Lake at the turn of the Ming and the Qing dynasties. As a result, some people mistake modern Nanyang Lake for Dushang Lake and think the emergence of modern Nanyang Lake much earlier. In fact, it was the blockage of its backward position that gave birth to the modern Nanyang Lake. This happened only about 250 years ago. At first, the area of Weishan Lake consisted of several lakes. As the governor of the Qing Dynasty took it as the most important water-supply place for the canal and set up strict rule of water control for it, Weishan Lake became a united big lake about 1740A. D. The lower terrain was another reason for its extension. These changes are considered related closely with the Huanghe River flooding, the canal route changing and the human activities.