Floating solar still is considered as a land-saving, easy-operating and environmental-friendly approach for freshwater production. However, the low yield and work instability in actual weather conditions limits its application. To overcome these disadvantages, a bionic floating solar still inspired by water intake of plant roots was presented in this paper. The channels for water supply were distributed in array and wrapped in a whole thermal insulation sheet. With the design of simulating roots, the present desalination system achieves low heat losses, water-absorbing uniformity and structural stability. Cellulose fabric and glass were separately selected as evaporation and condensation materials of the experimental prototype after preliminary test. The outdoor experiment was conducted in Xingtai, China, and the accumulated radiation in the test day was 21.96 MJ/m². The maximum evaporation temperature and daily freshwater yield reached 59.2 °C and 1.5 kg/m²/d, respectively, which were the highest in comparison with existing floating solar stills. Next, the effect of rolling motion on humid air flow inside the still was investigated by CFD simulation. The results of this study will contribute to the further development of floating solar still, as well as the application of such small-scale desalination technologies.