Abstract: The complexation reaction between niekel(Ⅱ ) and 1-(2-pyridylazo)-2-naphthol (PAN) in the presence of Triton X-100 micelles has been investigated spectrophotometrically by comparison with the results obtained from chloroform extraction method and “cloud point” phase separation method. The characteristic results obtained from these methods are quite agreeable. It is deduced that the Triton X-100 micellar phase plays the same role as the organic solvents for liguid-liguid extraction. However the micellar phase is pseudo-phase and may be regarded as pseudo-phase extraction.On the basis of spectrophotomctric, cloud point and solubility studies, it may be supposed that the phenolic hydroxy group of PAN is bound with the ether oxygen of the oxyethylene group by hydrogen bonding or forming complex with it.The Ni²⁺-PAN complex and hydrophobic portion of PAN molecule are incorporated into the hydrocarbon interior of the micelle.In the presence of Triton X-100 micelles the apparent stability constant of Ni²⁺-PAN is larger (K'_stab is 5.3×l0⁹ and that of solvent extract Ni²⁺-PAN system is 2.1×10⁹). But the reaction is not sensitized.