In recent years, conductive hydrogels have become popular substrates for flexible sensors because of their good mechanical properties, electrical conductivity, and biocompatibility. In this paper, the authors solved the key problem of complex preparation technology of hydrogels and prepared conductive polyvinyl alcohol/silver nanoparticles (PVA/AgNPs) hydrogels sensor with high tensile, high sensitivity, and high stability systems. They were prepared by a simple and efficient method of doping AgNPs into the three-dimensional network of PVA hydrogels. The sensor had a large draw ratio of over 500% and stability could be demonstrated by the consistency of electrical signals in 1000 cycles of stretching. The embedded AgNPs enabled the hydrogels to obtain good sensing performance. The excellent performance of sensors was also reflected by the sensing resolution of 0.5% deformation and the fast response time of 758ms. The PVA/AgNPs hydrogel sensor was used to common human behaviors, such as finger and wrist bending, swallowing, and nodding, which could transmit signals sensitively and stably. Overall, the excellent performances of the PVA/AgNPs hydrogels made it possible to be used in flexible wearable devices as sensors and help monitor human behavior.