A new complex have been synthesized by solvent method using pyrazole-3-carboxylic acid as ligand reacting with CoCl2?6H2O metal salt. The complex's structures was characterized by single-crystal X-ray diffraction. The complex crystalized in monoclinic system, group is P21/c, a = 5.0994(2) ?，b = 11.3955(5) ?，c = 9.3680(4) ?， α = 90?，β = 95.925(5)?，γ = 90? Co(Ⅱ) center six-coordinated by two carboxylate O atoms, two pyrazole N atoms, and two O atoms of two water molecules, producing a octahedral coordination environment. The interaction between complex and BSA was studied by UV–Vis spectra and fluorescence spectroscopy. The results showed that the interaction between complex and BSA were exquisite. The quenching process could be described with static quenching mechanism, with quenching rate constant being 3.54?012 L?mol?1?s?1, binding constant being 7.06154?05 L?mol?1 and binding site number being 1.2595.