A novel Co（Ⅱ） coordination polymer was hydrothermally synthesized and characterized. The crystal crystallizes in the monoclinic system, space group C c with a =1.772 59（4） nm, b = 1.150 00（10） nm , c =2.452 76（11） nm, β =92.723（3）°, V =4.994 3 nm 3, Z =4, R =0.080 9, wR =0.213 4. The polymer based on [Co（μ 4,4′ bipy）（4,4′ bipy） 2(（H 2O） 2] n linear chains was cross linked by the H bond bridge of Co—OH 2…4,4′ bipy—Co and π π stacking interaction, producing extended 2D ladder structure. The susceptibility of the polymer at variable temperature（2 0300 K） shows a weak antiferromagnetic interaction and implies that the polymer has the tendency of spin transition. Also, the result of surface photovoltage spectroscopy（SPS） reveals that the polymer has a significant photo electronic transferring property in UV Vis regions, which correspond to π π transition, L M charge transfer transition（shoulder） and d d transition of Co 2+ ion, respectively.
