After pinpoint all optimum conditions for extraction Cobalt(II) as ion pair association complex or chleated complex with complexing agent 1-[2-pyridyl azo] -2-naphthol which dimonirtrate λmax for complex extracted was (446nm.) more stable complex formation was at pH= 7 and 60 μg Co(II)/5ml with 1×10-4 M 1-[2-pyridyl azo] -2-naphthol[PAN] dissolved in chloroform and shaking time 10 minutes. The stoichiometry of complex extracted to the organic phase was 1:1 metal : PAN [Co(PAN)+Cl- ] or [Co(PAN)] +(Cl-).Extraction method was endothermic as well as thermodynamic parameters after calculated waΔsH ex= 0.0149 KJmol-, ΔGex= -58.81 KJ mol- and ΔSex= 176.55 J mol-. Synergism study show from the slope is appear there is one molecule of TBP or MIBK participated in the structure of complex extracted to the organic phase.