Abstract: Based on gridded Argo data during 2005~2009 provided by the Real-time Argo Data Center in China, the surface and deep ocean temperature of the ocean east of Taiwan are investigated. The results show that the North Pacific Subtropical Mode Water exists south of Japan. The authors put forward an idea of constant warm mode water, revealed its cause and vertical structure, and confirm it with SODA (Simple Ocean Data Assimilation) and WOA09 (World Ocean Atlas 2005) data. It can be concluded that there are three kinds of mode in different layers of the ocean east of Taiwan. Thus, the ocean east of Taiwan can be divided into three areas: tropical area, subtropical area and temperate area. By analyzing the thermocline of each area using thermocline profiles, permanent and seasonal thermoclines’ vertical distributions and seasonal variability are summarized. They authors provided explanations to these results.