A new Mn(II) coordination polymer, [Mn0.5(PHDI)0.5(DHTA)0.5]n was synthesized under hydrothermal conditions (PHDI = 1,10-phenanthroline-5,6-dione, DHTA = 2,5-dihydroxyl-1,4-terephthalic acid). Crystallographic data for 1: Monoclinic, space group C2/c, with a = 16.6224(12) Å, b = 11.2536(8) Å, c = 9.3621(7) Å, α = 90°, β = 97.7800(10)°, γ = 90°, V = 1735.2(2)Å3, Z = 8, C10H5Mn0.50NO4, Mr = 230.62, Dc = 1.766 g/cm3, F(000) = 932, μ = 0.820 mm−1, R1 = 0.0356, wR2 = 0.0753. The metal center Mn(II) is six-coordinated, in which two nitrogen atoms come from a chelating didentate ligand of the PHDI, and four oxygen atoms come from four different carboxylic acid ligands of the DHTA, forming a deformed octahedral geometry. The two metal Mn are connected by four single dentate coordination oxygen atoms of two carboxylic acid of the DHTA, and continue to extend in different directions to form an infinite three-dimensional network structure. Additionally, the O(3)–H(3)···O(1), O(3)–H(3)···O(2)i hydrogen bonds further stabilize the structure of 1. The IR, TGA behaviors, Luminescence and PXRD of 1 have been studied in detail.