This paper aimed at the use change of the bay, a dynamic axis-area analysis method was put forward on the basis of the complex and dynamic characteristics of bays. Firstly, a bay was seen as a systematic structure composed of four axes: baymouth, mean low-tide line, coastline, land boundary, and three areas surrounded by these axes, namely alongshore land area, tidal zone, and alongshore sea area, the coastline is the main axis of the structure. Secondly, due to the uncertain structure of bays, the location of axes were explored, a dynamic land range establishing method was brought forward according to the Dynamic Degree of the plantation and construction lands. Thirdly, the monitoring indicators of each component of the bay structure for their use change condition were analyzed. In the end of the paper, the change of Daya Bay in the east of Guangdong province was taken as an example. Multi-source data of 1980s and 2004 were used as data source, the exploitative change characteristics of main axis and each area were analyzed by the method, and the driving forces were also discussed. The dynamic axis-area analysis method can describe the change of bay locally and wholly, and is proved to be a good way to reflect the bay use change.