Multiferroic heterostructures made of ferromagnetic and ferroelectric constituents have potential applications in novel spintronic devices,such as magnetoelectric memory,if their magnetoelectric coupling (MEC) is strong.For the conventional metal/ferroelectric multiferroic heterostructures,however,the change of interfacial magnetic moment upon reversal of the electric polarization is often very small,which limits their application.Here,by using first principles calculations,we demonstrate a new pathway towards a strong MEC at the interface between the semihydrogenated graphene (also called graphone) and ferroelectric PbTiO3,which exhibits an undisclosed physical mechanism and significant improvement over the conventional metal/ferroelectric interracial magnetoelectric coupling.The magnetization in the graphone can be electrically switched on and off by reversing the polarization of PbTiO3,in which the change of carbon-oxygen bonding at the interface results in the disappearance/recovery of magnetization.Furthermore,ferroelectric polarization can stably exist at the ultrathin PbTiO3 layer less than one nanometer due to the sufficient screening of interfacial charge by graphone.The predicted strong magnetoelectric effect in the ultimately thin graphone/ferroelectrictric layers opens a new direction to the electric control of magnetism for high density and low-power memory devices.