Abstract: The coordination polymer _n was synthesized by hydrothermal method with flexible ligand 1,4-bis (2-methy limidazol-1-yl) butane,the transition metal cobalt salt and acid (H₂ada).The structure of the compound was determined by single-crystal X-ray diffraction.The properties of IR and UV were also characterized.The photocatalytic activity and the mechansim were investigated mainly.The results showed that the complex belongs to monoclinic crystal,P2/n space group.The results of catalytic experiments indicated that _n has a good degradation effect on methyl orange under ultraviolet light.