A novel two-dimensional coordination polymer [Ba-2(phen)(4)(tP)(2)](n), (phen = 1,10-phenanthroline, tp = terephthalic acid) has been synthesized with tp as bridge ligands and structurally determined by X-ray crystallography. The crystal belongs to the monoclinic system, space 3 group C2/c, with a = 18.877(4), b = 18.489(4), c = 15.658(3) angstrom, beta = 103.61(3)degrees, V = 5311.5(19) angstrom(3), C32H20O4N4Ba, M-r = 661.86, Z = 8, F(000) = 2624, mu = 1.542 mm(-1), D-c = 1.655 g/cm(3), the final R = 0.0228 and wR = 0.0554 for 6063 observed reflections (I > 2 sigma(I)). The structural analysis shows that each tp ligand bridges barium atoms to form a two-dimensional infinite layer. There are aromatic pi-pi stacking interactions between neighboring layers, and aromatic pi-pi interactions further extend such layers into a three-dimensional supramolecular framework.