Conductive hydrogels with exceptional mechanical properties have received extensive attention in flexible strain sensors. However, there is still a huge challenge in the preparation of hydrogels with high toughness, conductivity and frost resistance performance. In this study, the prepared PA-PAAM-CS (PPAC) composite hydrogels were obtained by incorporating phytic acid (PA) and chitosan (CS) into poly(acrylamide-co-stearyl methacrylate) (PAAM) polymer network. The as-prepared PPAC composite hydrogel has exhibited good mechanical properties, good electrical conductivity, frost resistance and good strain sensitivity. The flexible strain sensor assembled by the fabricated PPAC hydrogel can be used to detect human motion, including small and huge human motion, showing good sensitivity and stability in a wide temperature range. Meanwhile, the hydrogels based pressure sensors as writing board have exhibited good sensitivity to tiny changes in writing various letters. Therefore, the prepared hydrogel will have broad application prospects in wearable devices, electronic skin and multifunctional sensor components.