Abstract: The chemical structure of cation exchange resin of furoic acid was discussed on the infrared absorption spectra and ESR. The structure is regarded as a conjugating unsaturated C=Clinkage formed by the acidic cleavage of furan ring of furoic acaid nd condensation reaction of the cleavage compounds under certain conditions. Unpaired electrons of appreciable concentration have been found in the resin of furoic acid by means of ESRspectroscopy. The g factor of the spectra of resin of furoic acid was 2.0088. Hence, the electrons in resin would be expected to be unlocalized electrons which are stabilized via resonance in high conjugation. Therefore, the resin is semiconductive. According to the resistance-temperature characteristic of resin measured at various temperature, the resin is found to be an intrinsic semiconductor.The photoconductivity of the resin was measured under visible light and ultraviolet light at various voltage.