In the medical field, traditional sensors often face challenges such as discomfort during wear, signal attenuation, and complications arising from invasiveness. Gallium-based liquid metal flexible sensors, with their exceptional advantages including high conductivity, flexibility, and biocompatibility, have shown great potential in medical diagnostics. This paper focuses on four innovative applications and technological advancements of gallium-based liquid metal flexible sensors in medical monitoring: in terms of vital sign sensing, these sensors enable real-time continuous monitoring of dynamic physiological parameters such as pulse, respiration, and surface pressure, providing data support for early disease warning; for motor function sensing, they can accurately detect joint motion trajectories, swallowing coordination, and muscle strength, serving as a basis for rehabilitation assessment in neuromuscular disorders; in multi-parameter surface sensing, the sensors allow non-invasive detection of skin temperature and sweat composition, offering new technical pathways for early identification of health issues such as metabolic disorders; in deep electrophysiological signal sensing, they break through the limitations of traditional methods in collecting weak internal signals such as neural and EEG signals, offering new tools for the diagnosis and treatment of neurological diseases. This paper provides an in-depth analysis of the practical applications of gallium-based liquid metal flexible sensors in early disease warning, postoperative monitoring, rehabilitation management, and personalized medicine. It also summarizes the key challenges in real-world applications, including packaging reliability, multi-physics field signal crosstalk, and weak signal acquisition, and explores corresponding optimization strategies. Finally, the paper discusses the future research prospects of gallium-based liquid metal flexible sensors in the medical field.