A novel aromatic diamine monomer (4,4′-(dibenzofuran-2,8-diyl) dianiline (DFPDA)) derived from the rigid planar dibenzofuran was synthesized through Suzuki coupling reaction. The aromatic polyimide (2-methyl-6-(4-(8-(p-tolyl)dibenzo[b,d]furan-2-yl)phenyl)pyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone (DFPPI)) based on such new diamine DFPDA and pyromellitic dianhydride (PMDA) was prepared by two-step polymerization and subsequent thermal imidization. Compared with traditional polyimide (Kapton), the resulted DFPPI exhibits improved barrier properties with water vapor transmission rate and oxygen transmission rate which is 22.9 g m−2 day−1 and 20.7 cm3 m−2 day−1, respectively. Wide-angle X-ray diffractograms and positron annihilation lifetime spectroscopy reveal that the improved barrier properties of DFPPI are mainly due to the higher crystallinity and lower free volume of the polymer, which are resulted from the rigid planar structure. The DFPPI also shows excellent thermal stability and mechanical properties with a glass transition temperature of 427°C, 5% weight-loss temperature of 558°C, and tensile strength of 121.0 MPa. The polyimide has attractive potential applications in flexible electronics and high-grade packaging area.