Conductive hydrogels with high flexibility, superior formability, good mechanical elasticity, and excellent biocompatibility have emerged as promising materials for broad applications in flexible/wearable electronic devices. In this work, a conductive dual-network PVA/SA/MXene hydrogel (PSM-h) composed of polyvinyl alcohol, sodium alginate, and MXene (Ti3C2Tx) is constructed by a green method without using chemical crosslinking agents. The resultant hydrogel with dual-network feature shows excellent cytocompatibility (no toxicity for human umbilical cord mesenchymal stem cells), high stretchability (up to 263%), and superior anti-fatigue ability (stretched up to 1000 cycles). More importantly, PSM-h based strain sensor presents good sensing sensitivity with a fast response time (62.5 ms) and a low detection limit even under a very slight strain of 0.2%. In terms of the practical application, the PSM-h based strain sensor can be applied to detect and distinguish various human motions.