The interaction of poly(ethylene oxide) (PEO) with the ionic surfactants, sodium dodecylsulfate (SDS) and cetyltrimethylammonium chloride (CTAC) respectively, in aqueous solutions containing a certain concentration of NH4Cl, is studied by the viscosity measurement. It has been found that the ion-dipole interaction between PEO and ionic surfactants is changed considerably by the organic salt. For anionic surfactant of SDS, the addition of NH4Cl into solution strengthens the interaction between PEO and the headgroup of SDS. On the other hand, for cationic surfactant of CTAC, the interaction between PEO and the headgroup of CTAC is screened significantly by NH4Cl dissolved in solution. These findings may potentially be attributed to the negative property of the oxygen group of the PEO chain. In the presence of NH4Cl, the cationic ions of the organic salt bind to the oxygen group of the PEO chain so that PEO can be referred to as a pseudo-polyelectrolyte in solution.