Abstract: To improve the interfacial performance between aramid fiber and rubber matrix, this paper developed a strategy of in-situ growth of hyperbranched polysiloxane with double bonds onto the surface of aramid fiber. At first, the initial layer on the surface of fiber was established by the biomimetic modification of dopamine, and then, the middle layer was created by the graft of amino silane coupling agent via Michael addition reaction. Finally, the in-situ growth of hyperbranched polysiloxane was realized through the dehydration condensation reaction. The surface morphology and chemical structures of aramid fibers before and after modification were investigated by scanning electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. It can be obtained from the results of H pull-out tests of aramid fiber/rubber that the method proposed in this paper can increase the interfacial bonding strength by 66.4%, which can be ascribed to the improvement of surface roughness and the co-vulcanization between fibers and rubber. Furthermore, the graft of polydopamine initial layer makes this modification method have high universality and industrial application potential.