Abstract: Chengdu has a long history of water culture. The water conservancy construction in the city had extended from the ancient Shu and pre-Qin, Ming Dynasty to Qing Dynasty. It has given impetus to the prosperity of several generations. Tang Dynasty and Song Dynasty are the most important stage for the change in the internal water system of ancient Chengdu. Due to the large-scale construction at the Tang Dynasty, the structural system featured by ‘the city being embraced by two rivers externally and one pond connecting two internal rivers’ has gradually formed. During the Song Dynasty, some repair and renovation were made, thus leading to the densely-concentrated water channel network and the maturity of urban water conservancy system. Under this background, river course had extended beyond its basic functions to become a natural landscape bounding the city. Most of gardens were built along water system, creating a large-scale public natural space. The overall environmental landscape of the city had been also formed with the water network system, which had pushed forward the change of internal natural system. After analyzing the interactive relationship between water conservancy construction and the city during Tang and Song Dynasties, this paper has discussed the internal connection and profound influence of water network and natural system. According to the planning methods released in Chengdu, this paper has made some reflection after taking the current status and historical experience of inland rivers into consideration.