A large-scale patterned Cu micro-nano structure was prepared via laser ablation technology in liquid. A Si wafer was used as the substrate， which was immersed in an ethanol solution containing Cu₂O microparticles and processed by a nanosecond pulsed laser. The effects of the laser power， scanning speed， and number of scans on the Cu micro-nano structure in liquid， the formation mechanism of the patterned Cu micro-nano structure， and the wetting characteristics of the patterned Cu micro-nano structure were analyzed. The results of scanning electron microscopy indicated that with increases in the laser power， scanning speed， and scanning time， the melting of Cu particles in the patterned Cu micro/nanostructure intensified， the particle size of nanoparticles in the center of the laser spot increased， and a micron unit structure was formed at the junction of the laser spot， exhibiting a periodic distribution. Energy-dispersive X-ray spectroscopy confirmed that a small amount of Cu was distributed in the central region of the spot， and a large amount of Cu was concentrated at the junction of the spot. In addition， both the surface roughness and static contact angle of the sample increased with the number of scans. When the number of scans was 6， the average surface roughness， water contact angle， and oil contact angle are （1.3±0.11） μm， （155.2±1.5）°， and （100.0±1.3）°， respectively. The proposed simple and rapid preparation method for large-area patterned Cu micro/nano structures has wide application prospects in the fields of microfluidic chips， water-collection systems， and wastewater treatment.