A humidity sensor driven by self-powered graphene oxide film with in-plane proton transfer was successfully fabricated. A 5 x 5 humidity sensor array was built, and finger position was detected via monitoring the humidity change under zero bias voltage. Delta I/I-0 was about 45 at finger distance of 0.8 cm, and reached 450 at distance of 0.2 cm. The facile device preparation procedure and fast current pulse upon exposure to moisture make it suitable for practical applications in smart self-powered humidity sensor systems.