A water solar lamp comprises a light transmissive casing, a solar panel, a power processing unit, and a plurality of light emitting components. The light transmissive casing comprises an upper cover, a base assembled with the upper cover, and an installation space defined by the upper cover and the base. The base is set as a water-facing side, the base comprises a ring groove for temporarily storing gas when the light transmissive casing is disposed on water, and the ring groove divides the base into an inner ring region and an outer ring region. The solar panel is disposed on the upper cover, and the power processing unit is disposed in the installation space and connected to the solar panel. The plurality of light emitting components are disposed in the installation space, and the plurality of light emitting components receive power provided by the power processing unit to emit light.