Abstract: With the unprecedented development of navigation practice, the knowledge framework that “Tianxia”(“天下”, world) consists of “Jiuzhou”(“九州”, land) - “Sihai”(“四海”, four oceans) was gradually broken and forgotten by navigation practice in Song and Yuan Dynasties. The marine geospatial cognition changed from abstract “Hai”(“海”) to concrete “Yang”(“洋”). “Hai” was divided and named different “Yang” in various ways. Division and naming of these “Yang” were still regional knowledge. However, knowledge of “Yang” generated in navigation practice, which laid a logical foundation for different dynasties and countries to form common marine knowledge and concept. In the process of China accepting and integrating into common marine knowledge and concept of the world, the unprecedented development of ocean practice in the Song and Yuan Dynasties opened a turning stage.