A facile and versatile strategy was developed for the preparation of self-healing hydrogels containing double networks of both physically and chemically cross-linked polymers. The autonomous self-healing of the hydrogel was achieved through the dynamic bonding of physical cross-linking and the migration of ferric ions. The self-healing of hydrogel is repeatable, and does not decay after many cycles of cutting and healing process. We further demonstrated that the self-healing hydrogel can be used as protective coatings that are capable of repairing themselves from mechanical damage. The self-healing hydrogel material may find applications in smart coatings, soft robots, and biomedical devices.