The work aims to utilize low-temperature plasma to induce the rapid curing of copper complex inks, fabricate highly conductive copper films on flexible substrates, and illustrate the effects of solvent ratio, preheating treatment time, plasma power, and treatment time on the curing structure and conductivity of the copper film. The copper loading of the ink and the thickness of printed films were adjusted by changing the solvent ratio in the ink. The low-temperature curing process was optimized by controlling the variables. The physical characteristics of the obtained flexible films were characterized with scanning electron microscope, confocal microscope, and resistivity measurement. The applicability of the developed copper ink and the process in flexible electronics of printing was tested through ball-point pen direct writing and roll-to-roll printing. Flexible copper films with the thinnest thickness of 40 nm and the lowest resistivity of 3.76 μΩ∙cm could be fabricated by the synergistic optimization of the ink formula and plasma treatment. Plasma treatment can be utilized to realize the rapid curing of copper complex inks at a low temperature and fabricate high-performance copper films, which shows massive application potential in printed flexible electronics.