Studies on flexible electrodes are critical to the development of flexible energy storage devices for emerging wearable electronic products. Flexible H2V3O8 nanobelts/reduced graphene oxide (H2V3O8/rGO) electrodes were prepared by hydrothermal method and subsequent vacuum filtration. Detailed morphology and composition characterization demonstrated that the as-prepared H2V3O8/rGO electrode displayed network structure and the surface composed of cross-linked H2V3O8 nanobelts. The content of V5+:V4+ in flexible H2V3O8/rGO electrode was close to the theoretical ratio of 2:1. Additionally, a series of electrochemical test results indicated that the flexible electrode exhibited excellent electrochemical performance even at high mass loading of 8.3 mg cm(-2). The flexible electrode showed specific discharge capacity of 377 mAh g(-1) at a current density of 0.1 A g(-1) and high energy density of 558 Wh kg(-1) at a power density of 227 W kg(-1). Meanwhile, the flexible H2V3O8/rGO electrode exhibited excellent mechanical and electrochemical properties when applied to flexible lithium ion batteries.