Micro-nano structured functional surface is a hot topic in surface engineering research, and sub-wavelength structures have better anti-reflective properties. Geometric parameters of micro-nano structure on silicon surface are calculated by using equivalent medium theory. Then the above optical model structure is established based on finite element simulation and the optical properties are simulated using COMSOL Multiphysics commercial software to study the effect of reflection reduction in the long-wave infrared (8~12 μm) range, and the effects of surface morphology and structural feature size on the transmittance are analyzed separately. According to the simulation results, it is concluded that the period of the micro-structure dominates its surface transmittance change. Under the condition that other structural parameters are consistent, changing the height can increase the transmittance in a small range. The transmittance of trapezoidal micron structure is higher than that of conical and square cylindrical; there is no obvious effect of reflection reduction of nanostructure in infrared band. The effects of period, microstructure height and duty cycle on the surface tension of zone-melted silicon are studied by analyzing the theoretical model of wettability, and it is found that the change trend of static contact angle of microstructure surface is positively correlated with height, and negatively correlated with cycle and duty cycle. The micron structures with a period of 6 μm are formed by the Radical Plasma Source (RPS) etching technique at an etching gas flow rate of CF₄∶O₂∶Ar = 400∶200∶20, a microwave power of 2 000 W, an operating air pressure of 125 Pa, and an etching time of 150 s. On this basis, the dot, stripe and cone nanostructures are fabricated by low-energy ion beam etching (LE-IBE) with ion beam incidence angles of 60°, 60° and 75°, incidence energies of 400 eV, 600 eV and 400 eV, ion beam currents of 50 mA and etching times of 60 min, respectively; finally, the antireflective and self-cleaning nanocomposite structures are fabricated on the zoned silicon surface. The final micro- and nanocomposite structures with anti-reflection and self-cleaning functions are prepared on the fused silicon surface.The surface morphology of the fabricated micro- and nanocomposite structures with different morphologies of period 6 μm is examined using an Atomic Force Microscope (AFM).The optical and hydrophobic properties of the fabricated silicon surface micro- and nanocomposite structures are characterized using a Thermo Scientific Nicolet iS20 Fourier infrared spectrometer and a JC2000D2A contact angle meter, respectively, with a transmittance of 78% and a static contact angle of 125.77°. In addition, further analysis of the resulting structure shows that the transmittance of the micro-nano composite structure in the long-wave band is slightly larger than that of the micro-structure, and the nanostructure with lower height has no significant effect in the infrared band to reduce the reflection, while the micron structure achieves the dominant role in the infrared band to reduce the reflection; The contact angle of micro-nano composite structure is larger than that of single micro structure or nano structure, consistent with the theoretical simulation results, which shows that the presence of micro-nanostructures can effectively improve the hydrophobicity of the silicon surface. Through theoretical simulation, experimental preparation and characterization, the anti-reflection and hydrophobic properties of sub-wavelength micro-nano composite structures are analyzed, providing new processing techniques and ideas for surface modification of micro-nano structures, and expanding the application of zone-melted silicon in the field of long-wave infrared.