PE, one of the main materials for the general-purpose separator of lithium-ion battery, causes heat shrinkage of about 10% at 120°C and up to 37% at 160°C, so it is regarded as one of the most important factors affecting safety, such as battery short circuit. Among several reported separator materials that could replace commercial separators of lithium-ion batteries(LIBs), aramid nanofiber (ANF) is considered one of the promising separator materials due to its excellent mechanical properties and thermal stability. In this study, an aramid separator was prepared by applying the electrospinning method. Polyethylene oxide (PEO) was mixed as a carrier-polymer because the aramid solution has high viscosity and is difficult to electrospun alone. Solubility was evaluated for the homogeneity of the solution, and the rheological characteristics of the solution were evaluated to determine the supply ratio suitable for electrospinning. As a result, a porous membrane structure made of aramid composite nanofibers was fabricated.