In recent years, the energy consumption of data centers increases rapidly. Above 30% of the total energy use in a data center is consumed by the cooling equipment. Free cooling and distributed cooling are the main methods of cutting down this part of consumption. Loop thermosyphon with multiple evaporators in parallel arrangement can utilize natural cold source and simultaneously achieve rack level or chip level cooling. Therefore, it has good application potential in data centers while its performance is lack of investigation. In this paper, a thermosyphon loop with dual evaporators, many parts of which are transparent, is investigated experimentally and visually. The startup process and steady-state operation under different heating conditions are studied. Also, the internal flow of each evaporator is observed and recorded. The results shown that under different heating power, the larger the difference of heating power, the larger the temperature difference. The startup time of one evaporator is longer when the other evaporator does not have heating power input, compared with heating power input is applied on the other evaporator. Churn flow is observed at the outlet and the height of the liquid surface oscillates periodically. This paper is helpful for the design and application of loop thermosyphon with multiple evaporators and will promote the energy-saving of data center cooling.