In extreme environments, flexible sensors represent a cutting-edge technology that can substantially expand the horizons of human perception, serving as a crucial "technological safeguard" for safety measures. Among these, hydrogel sensors stand out due to their remarkable flexibility, tunable physicochemical properties, and consistent biocompatibility. These sensors are capable of transforming external changes in stretch, pressure, temperature, and other factors into detectable signals, thereby enabling a wide range of applications, including motion tracking and human-machine interaction. Nevertheless, conventional hydrogel sensors are susceptible to dehydration and breakage under extreme conditions of high temperature, high salinity, and intense cold. This vulnerability stems from the presence of abundant "free water" that readily escapes and a sparse polymer chain crosslinking structure, ultimately leading to a decline in performance or even complete failure.