In this work, the preparation of Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /graphene oxide (GO) nanocomposite and its application in radio frequency (RF) on-chip transformer was investigated. The Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /GO nanocomposite was synthesized by using solvothermal method in the presence of GO and integrated into an on-chip transformer by using a novel post-CMOS process. The experimental results show that the Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> nanoparticles (with ~13 nm in diameter) are uniformly attached onto the surface of GO and the nanocomposite exhibits typical ferromagnetic behavior. Compared with the identical structural air-core transformer, the inductance (L), quality factor (Q), and coupling coefficient (K) of the device with Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /GO nanocomposite film are increased by 28%, 24%, and 11% at 1 GHz, respectively. The enhancement effect of the magnetic film on the RF performance of the transformer has been maintained until 2 GHz. It is believed that Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /GO nanocomposite has great potential application in RF on-chip transformers with operation frequency below 2 GHz.