The invention relates to a floating body cooling device. The floating body cooling device comprises a shell, a heat dissipation pond, a temperature sensor, a processor and a control circuit. The shellis internally provided with a cooling pipeline in a repeatedly-bent shape; a water inlet end opening and a water outlet end opening of the cooling pipeline are formed in the two sides of the upper end of the shell correspondingly and communicate with the two ends of the heat dissipation pond through pipelines correspondingly; a water pump is arranged on the pipeline between the water outlet end opening of the cooling pipeline and the heat dissipation pond; the temperature sensor is fixedly placed at a water inlet of the water pump and connected with the processor through a line, the processoris connected with the control circuit through a line, and the control circuit is connected with the water pump; and a floating body is arranged in the heat dissipation pond, floats on liquid in the heat dissipation pond and is made of an aluminum material. Compared with the prior art, automatic water replacement is conducted according to the detected temperature, environmental friendliness and energy saving are achieved, and the cooling effect is good; and the floating body can take a heat dissipation effect on the liquid and can further buffer a water flow so as to avoid overflowing of the liquid, and the heat dissipation efficiency is high.