Conductive hydrogels (CHs) for flexible bioelectronic devices have raised great attention due to their tunable mechanical performances, adhesion, anti-swelling, and biocompatibility. This review summarizes the current development of conductive hydrogel-based flexible bioelectronic devices in the aspect of classifications and applications. Firstly, the conductive hydrogels are classified into two kinds according to the types of conductivity: ionic conductive hydrogels and electronic conductive hydrogels (hydrogel based on pure conductive materials, introducing conductive micro/nano-materials). Secondly, the applications of conductive hydrogels for bioelectronic device, like wearable devices (strain sensor, body fluid detector, serviced in extreme environment), tissue engineering (skin, heart, nerve, muscle), and other applications (bionic robot, cancer treatment), are highly illustrated. Finally, a depth outlook is given, which aims to promote the development of this field in the future.