The interactions between Pluronic block polyethers (L64 and 17R4) and cetyltrimethyl ammonium bromide (CTAB) were investigated by the measurement of the interfacial dilational viscoelasticity. The dilational moduli of the Pluronic block polyether/CTAB solutions firstly increased, passed through the maximum, and then decreased with the increasing concentration of CTAB. 17R4/CTAB mixed solutions have much larger dilational moduli than L64/CTAB systems, which means that 17R4 and CTAB have stronger interactions than L64 and CTAB. The dilational moduli of 17R4/CTAB systems were different from L64/CTAB systems in the presence of NaBr. The dilational moduli of the L64/CTAB mixed solutions decreased firstly, passed through the minimum value, and then increased with the increasing concentration of NaBr, while the dilational moduli of 17R4/CTAB mixed solutions increased firstly, passed through the maximum, and then decreased. These differences show that NaBr has great influence on the interactions between Pluronic block polyethers and CTAB.