Charge carrier modulation of graphene using the ferroelectricity of a nearby dielectric can be useful for controlling the electronic properties of graphene. However, when graphene is located on ferroelectric oxides, their electrical coupling frequently shows abnormal behaviors, such as anti-hysteresis, in field-effect transistor operation. From the systematic examination of graphene on a ferroelectric oxide single-crystal [Pb(Mg1/3Nb2/3)O3]1-x–[PbTiO3]x (PMNPT) substrate, we observed that the ferroelectric modulation of graphene was significantly influenced by the ambipolar nature of graphene and ferroelectric-assisted charge trapping with carrier-type dependency. For graphene/hexagonal-BN on the PMNPT, the Coulomb interaction between charges in interfacial traps and ferroelectric polarization seems to decouple the graphene conductance from the polarization field and induce only the charge trap effect on device performance. Consequently, the asymmetric surface charge compensation of ferroelectric oxide by the ambipolar graphene channel determines the detailed coupling process between the charge carrier of graphene and ferroelectric polarization, resulting in direct ferroelectric coupling or indirect anti-hysteretic coupling.