Nest-shaped cluster [CuBr(bpy)2][MoOS3Cu3Br2(bpy)] was synthesized by the treatment of (NH4)2MoO2S2,CuBr and Et4NBr with bpy (2,2'-bipyridyl) in CH3CN. Its structure has been characterized by X-ray diffraction:monoclinic,space group P21/n, with a=1.0092(4), b=2.6347(7), c =1.4087(3) nm, β = 91.744(9)°, V=3.7438 nm3, Z=4,and final R=0.051, Rw=0.053. It consists of two parts:nest-shaped structural unit [MoOS3Cu3Br2(bpy)]- and complex ion [CuBr(bpy)2]+. We determined its third-order nonlinear optical (NLO) properties with a 7-ns pulsed laser at 532 nm. The cluster exhibits strong NIO refractive behavior, its third-order susceptibility X(3) was calculated to be 2.7× 10-11esu in a 7.8×10-4 g/cm3 DMF solution.The value is comparable to those of inorganic clusters.