The foot of the continental slope is an important topographical feature of the continental margin. Its the basis for coastal states to extend its continental shelf rights and to delimit the outer limit of the continental shelf beyond 200 nautical miles. Its also an important technical parameter that the Commission on the Limits of the Continental Shelf pays special attention to when considering the submissions of coastal states. The formulation of the continental shelf regime in Article 76 of the United Nations Convention on the Law of the Sea originates from the typical passive continental margin. However, due to the diversity and complexity of the global continental margin, especially the transformation and influence of late tectonic activities and sedimentation on the continental margin, the seabed topography is extremely complex and changeable, which makes it very difficult to identify the foot of the continental slope. In addition, in order to obtain the largest extent of the outer continental shelf, each coastal state has interpreted the relevant provisions of the foot of the continental slope in their own favor, making the foot of the continental slope a hot and controversial issue in the delimitation of the outer continental shelf. Based on the provisions of the United Nations Convention on the Law of the Sea and the "Scientific and Technical Guidelines of the Commission on the Limits of the Continental Shelf" on the foot of the continental slope, combined with the geological characteristics of different types of continental margins and the delimitation practice of various coastal states, the determination of the base of the continental slope, the selection of the point of greatest change and the application of the evidence to the contrary are discussed.