Abstract: The mica nanosheets (MNSs) were prepared by high-speed mechanical ball milling as the reinforcement, and introduced into the splitting process of aramid fibers. The aramid nanofibers (ANFs) were prepared in a dimethyl sulfoxide/potassium hydroxide (DMSO/KOH) system. ANF/MNS composite films were prepared by vacuum-assisted filtration, and the effect of MNS content on the mechanical properties of ANF films was investigated. It gains the best mechanical properties and insulation properties when the MNS content is 0.041wt%. The tensile strength is 249.3 MPa, the toughness is 36.7 MJ·m⁻³, and the dielectric breakdown strength is 46.2 kV·mm⁻¹. They increased by 45.1%, 197.1% and 60.0% compared with the pure ANF films, respectively. Nanoscale MNS can form strong interfacial interaction with ANF, and the inherent strength of MNS also contributes to the improvement of the mechanical properties of nanofilms.