Abstract: Wingtip vortex is an important part of the civil aircraft wake vortex, which not only induces drag and affects the economy of the aircraft, but also causes the wake encounter problem and affects the safety of the follow-up aircraft. With the advancement in numerical simulation and experimental measurement techniques, the understanding of the wingtip vortex structure characteristics, dynamic characteristics, instability development, evolution and other phenomena and mechanisms have been deepened, and various research results have been obtained. In recent years, with the development of instability theory and modal analysis methods, researchers have studied the instability and modal characteristics of wingtip vortices, trying to reveal the law and mechanism of the instability evolution, with the hope to establish a flow control strategy based on instability to achieve the optimal control to accelerate the attenuation and dissipation of wingtip vortices. This study reviews the research on wingtip vortex instability and its modal characteristics. We firstly introduce the instability characteristics of wingtip vortices, then compare the basic principle of typical modal analysis methods, and then analyze the wingtip vortex instability and its modal structure characteristics. Finally, the research status and remaining issues of wingtip vortex instability modal analysis are discussed.