The nonlinear optical properties of the AgOx-type super-resolution near-field structure (SuperRENS) films were studied using confocal Z-scan technique with 0.7 ns, 532 nm laser pulses. Nonlinear refractive indexes at different laser power were obtained through close-aperture Z-scan and compared with the measured results of Au film and Ag film, The mechanisms of this change due to the photochemical reaction, thermal effects and optical response were discussed. The experimental results show that heat by laser illumination causes a phase transition, so results in the enhancement of the localized surface plasmon of dissociated Ag nanoparticles.