To address the issue of inaccuracy in signal detection due to excessive reliance on adhesives when traditional hydrogels were utilized as flexible strain sensors, a type of hydrogel with high adhesion, namely polyacrylic acid/2-amine-2-methylpropanesulfonic acid/hydroxyethyl methacrylate (p(AA-AMPS-HEMA)), was fabricated and employed in flexible strain sensors. The findings indicate that the hydrogel not only demonstrates outstanding mechanical properties (with a tensile stress of 195.02 kPa and a tensile strain of 1193.55%) and remarkable adhesion (the adhesion strength to pig skin can reach 38.94 kPa), but also possesses stable and sensitive sensing characteristics. It is further assembled into a flexible strain sensor, which can precisely capture and monitor various human movements such as finger bending, wrist movement, and knee bending. The hydrogel exhibits a promising application prospect in the domain of intelligent sensing.