The invention relates to a riverway navigation mark light which utilizes water fluctuations for power supply, and is characterized in that the riverway navigation mark light comprises a support (1), a navigation mark float (2) and an upper floating drum (5) are arranged at the lower part of the support (1), the navigation mark float (2) is positioned at the central position of the support (1), a coil (3) is arranged in the middle part of the upper floating drum (5), a magnet (4) is movably arranged in the upper floating drum (5), the lower end of the magnet (4) is connected with a lower floating drum (6), a storage battery (7) is arranged at the upper part of the support (1), and the battery (7) is connected with a navigation mark light (8) which is fixed on the support (1) by a conducting wire. The riverway navigation mark light has the advantages of environmental protection, energy conservation, simple and practical structure, long power supply time, low cost and convenient production and use. The riverway navigation mark light improves the existing navigation mark light and utilizes energy generated by the water fluctuations of a navigation channel to be converted to electric power to be used for the navigation mark light, thereby having wide range of application.