In this study, a novel, highly efficient, and magnetically responsive demulsifier, namely, Fe3O4@hyperbranched polyamidoamine-graphene oxide (MKh-GO), was synthesized. First, Fe3O4 was synthesized, and Fe3O4 was wrapped in hyperbranched polyamidoamine (h-PAMAM) by gamma-(methacryloyl oxide) propyltrimethoxysilane (kh570), and MKh-GO was synthesized by condensation reaction. The chemical structures and morphologies of the samples were characterized by Fourier transform-infrared spectroscopy (FTIR) and transmission electron microscope (TEM). The magnetic response of the sample was tested by vibrating sample magnetometer (VSM). The MKh-GO was used to separate crude oil in water emulsion; the effects of MKh-GO dosage, temperature, and pH value on the demulsifying efficiency were investigated. Possible demulsification mechanisms were summarized. The results show that MKh-GO is successfully synthesized, and MKh-GO exhibits excellent demulsification performance; MKh-GO is recycled seven times, and the demulsification efficiency is 97%.