A macroporous polyarylate (PAR) layer was formed on a polyethylene (PE) separator from coating solutions containing PAR, tetrahydrofuran (THF) as the solvent; and various alcohols (or diols) as nonsolvents via nonsolvent-induced phase separation (NIPS) process. The effects of the nonsolvent molecular structure and its content on the morphology of the coating layer were explored. Droplets grew by a coarsening process after the onset of phase separation by solvent evaporation, and then leveled off at a fixed droplet size. The final pore size increased with the molecular weight Of the alcohol (or diol) when the composition of the coating solution was fixed. It increased as the nonsolvent content in the coating solution increased, while it decreased as the PAR content in the coating solution increased. The meltdown temperature of the separator increased with the, macroporous PAR coating, while air permeability of the separator was reduced with the coating: Changes in the meltdown temperature and air permeability depended on the morphology of the coating layer.