Sail systems and aerodynamic performance are important factors for determining the dynamic performance of unmanned sailboats. First, in order to identify the future trends of the flexible sails of unmanned sailboats, representative unmanned sailboats with flexible sails in the world are reported. The flexible sail system is then summarized in terms of physical characteristics, installation and fixing schemes, and sail trim schemes. The progress of three research methods of numerical simulation, wind tunnel test and sea trial for aerodynamic performance are analyzed respectively, and the basic technical route for research on the aerodynamic performance of flexible sails is summarized. Finally, several future key technologies of unmanned sailboats and flexible sails are predicted.