Aiming at the problems of easy water loss, limited application scenarios and poor biocompatibility of traditional hydrogels for flexible strain sensors, a highly humectant acrylamide/lithium bis(trifluoromethane)sulfonimide/graphene oxide/methyl methacrylate hydrogel (LAGM) by one-pot photopolymerisation has been successfully prepared and applied in the field of flexible strain sensing. Firstly, acrylamide and bis(trifluoromethane) were prepared as deep eutectic solvents with a certain molar ratio. Then, graphene oxide aqueous solution was added to form a‘deep eutectic solvent-in-water’structure. Further, the methyl methacrylate, a hydrophobic monomer, was introduced to form a hydrogel by photopolymerisation. The results show that the hydrogel not only exhibits excellent mechanical properties (tensile stress: 2934.73 kPa, tensile strain: 419.39%) and excellent moisture retention (only 2.42% weight loss at equilibrium), but also possesses stable and sensitive sensing properties. The assembly is further applied to flexible strain sensors, which can not only accurately capture and monitor human motion, but also be stably applied to the detection of human electrocardiographic, electromyographic, and electrooculographic signals. This research result not only solves the above defects of traditional sensors, but also provides a new solution for the future development of flexible wearable devices.