Femtosecond laser direct writing technique is used to fabricate microelectrodes on flexible substrates with a cheap copper ion pre-coating. The copper nanoparticles are obtained using laser-induced reduction and in situ bonding, and the as-written copper electrodes exhibit excellent electrical conductivity. Further, the effects of laser power and scan speed on the microstructure and electrical conductivity of the electrodes are studied. The results denote that the conductivity generally increases with the increase of laser energy density. The obtained copper electrodes are mostly network-like metallic copper and exhibit the lowest sheet resistance of 2.74 Ω·sq ^-1 at a laser power of 1210 mW and a scan speed of 1 mm/s. This research provides a new technique for developing low-cost and high-efficiency flexible devices, which can benefit the application of copper nanomaterials in the electronics industry.