Investigation on the adsorption of proteins on graphene is very important for the biomedical applications and safety evaluation of graphene materials.In this work，the adsorption of cytochrome c，a protein involved in cell apoptosis，on graphene oxide was studied.The morphology of graphene oxide and its protein complex were characterized by atomic force microscopy，indicating that the adsorption occured in multilayer mode.The adsorption kinetics and isotherm were also studied，revealing a very high adsorption capacity(1 978 mg/g) of cytochrome c on graphene oxide.Finally，it is found that the enzymatic activity of cytochrome c only changed slightly before and after the adsorption on graphene oxide，suggesting that the conformation of cytochrome c was maintained during the adsorption process.This work is expected to provide some important data for biomedical applications and safety evaluation of graphene materials.