Abstract: The present invention discloses a flexible graphene film and a preparation method thereof. The preparation method includes steps of placing a liquid graphene oxide film in a poor solvent, performing gelation, and drying a graphene oxide gel film. The graphene film has an excellent flexibility, a crystallinity of lower than 60% and an elongation at break of 15-50%, wherein no crease is remained after the flexible graphene film is repeatedly folded more than 100,000 times. The preparation method of the graphene film provided by the present invention controls the macroscopic properties of the graphene film by microscopically controlling the morphology of the graphene monolith, and can significantly improve the flexibility of the graphene film. It can significantly improve the flexibility of the graphene film. The process is simple and easy to be popularized, and has potential applications in flexible electronic devices and the like.