For the porous membranes prepared from a calcium chloride-methanol solution of nylon-6, the behaviors of melting and recrystallization were investigated by DSC measurements. For thin samples annealed at 200degreesC, a double peak was observed on the DSC curve. Further immersing them in an aqueous solution of calcium chloride or magnesium chloride and then drying, the higher side peak intensity decreased with the immersion time and disappeared finally. The residual single peak temperature for samples with magnesium ions was 7 degreesC higher than those with calcium ions, reflecting the increase of three structural units of crystal length during the heating process. The structural models adsorbed calcium and magnesium ions are proposed.