The crystal of the title complex Mn(nip)(H₂O)₅ ( nip=5-nitroisophthalate ) was synthesized, and cultured in the filtrate of the reaction mixture. The X-ray single crystal diffractometer with graphite monochromated MoK_α (λ= 0.71073Å), elemental microanalysis, FT-IR, DSC and TG-DTG techniques were used to characterize the structure and thermal behaviors of the title complex. The results show that the central Mn²⁺ cation coordinates to the ligands 5-nitroisophthalate and 5H₂O in a distorted octahedral pattern. And the title coordination compound loses its five water molecules at the first step and the 5-nitroisophthalate at the second step during heating based on the thermal analyses and FT-IR data.