Polyaspartic acid/poly (acrylamide-acrylic acid) (PASP/P(AA-AM)) hydrogel matrix was prepared by introducing PASP into the poly (acrylamide-acrylic acid). A new type of double ion cross-linked PASP/P(AA-AM)/FeCl3 (PAAF) hydrogel with a high strength, super stretch, and better sensitivity was obtained through immersing the above matrix in FeCl3·6H2O aqueous solution. The introduction of Fe3+ can not only improve the mechanical properties of PAAF hydrogel, but also endow excellent sensing properties. The obtained hydrogel sensor shows excellent tensile properties (1125%), good mechanical strength (802.97 kPa), excellent fast self-healing performance (almost complete recovery), good fatigue resistance, and good sensitivity (GF is 3.04), which could detect the different human movements (such as fingers, elbows, and knee joints) with good stability under both small and large strains. The obtained PAAF hydrogel can be used as wearable flexible sensor to monitor human movements.