The present invention relates to a method for preparing graphene from a biomass-derived carbonaceous mesophase, which includes: soaking a base substance into an ethanol solution of a biomass-derived carbonaceous mesophase; after a certain period of time, taking out and drying the base substance, a layer of biomass-derived carbonaceous mesophase film being attached to the surface of the base substance; subjecting the base substance to a heat treatment under the protection of a hydrogen atmosphere, then a stacked graphene film was formed on the surface of the base substance; and further subjecting the base substance to ultrasonic dispersion in an alcohol solvent to separate the graphene film and the base substance, then a graphene alcohol was formed. The preparation process of the present invention is easy to implement. The raw material biomass-derived carbonaceous mesophase has abundant sources and is low in cost. The preparation process has low energy consumption, and is applicable to mass production. The obtained graphene film and graphene alcohol can be used in solar cells, nano-electronic devices, sensors, and so on, and have broad market prospects.