Super resolution near-field structure (super-RENS) is one of the most promising candidates for the ultrahigh-density optical storage, and near-field optical properties of the mask layer in super-RENS optical disk are crucial for its optical storage performance. The near-field distribution through the eutectic alloy mask layer has been studied by using three-dimensional finite-difference time-domain (3D-FDTD) method. Simulation results indicate that the periodic micro-/nano-structures formed in the eutectic binary alloy films after or during irradiation of a laser beam will result in a prominent near field enhancement and may be the origin of the higher signal-to-noise ratio (SNR) in super-RENS optical disk.