A new 4-chlorobenzoic acid bridge Co(Ⅱ) complex [Co2(2,2’-bpy)2(μ-L)2(L)2(μ-H2O)] (HL=4-chlorobenzoic acid) has been obtained by hydrothermal synthesis,and X-ray single-crystal diffraction analysis shows that it crystallizes in the monoclinic system,space group C2/c with a=22.537(5),b=16.212(3),c=15.306(3) ,β=124.37(3)°,V=4616.1(16) 3,Mr=1070.45,Dc=1.540 g/cm3,Z=4,μ=1.012 mm-1,F(000)=2176,the final R=0.0338 and wR=0.0810. The title complex is composed of dinuclear [Co2(2,2’-bpy)2(μ-L)2(L)2(μ-H2O)] molecules. Each Co(Ⅱ) atom is coordinated by two nitrogen atoms from one 2,2’-bipyridine ligand,three oxygen atoms from three 4-chlorobenzoic ions and another oxygen atom from one water molecule. The two Co(Ⅱ) atoms are connected by two 4-chlorobenzoic ions and one bridged water molecule. The dinuclear molecules are interlinked by hydrogen bond and π-π stacking interactions into a three-dimensional supramolecular network.