Abstract: Poly m-phenylene isophth alamide(PMIA) was synthesized using m-phenylenediamine and isophthaloyl chloride as monomers, 2-methylpyridine as acid binding agent by the low-temperature solution polymerization in N, N-dimethylacetamide (DMAc). Porous PMIA membranes with different pore structures were then prepared by non-solvent induced phase separation, and ethanol was used as non-solvent coagulation bath. The structures of PMIA were characterized by Fourier transform infrared and <sup<1</sup<H-nuclear magnetic resonance. The influence of polymer concentration on the pore structure and dielectric constant of the porous PMIA membrane was studied. Results show that when the concentration of PMIA is 21%, 17% and 15%, porous membranes with regular pore morphologies can all be obtained. Their dielectric constants are 2.31,2.07 and 1.89 respectively at 1 MHz, decreased by 63%, 67% and 70% than 6.22 of PMIA standard membrane.