In this paper, to enhance the adhesion between the copper pattern and flexible substrate, the silane coupling agent was added in the copper nano-ink with respect to the weigh fraction of silane. After then, the PI(Polyimide) substrate was treated by oxygen plasma. To investigate the effect of the plasma treatment, the AFM(atomic force microscope) were performed. Also, the copper pattern sintered by flash light was observed using SEM(scanning electron microscope). The adhesion test using the pressure sensitive tape was performed to measure the adhesion strength between the copper pattern and the substrate. The bending fatigue characteristic of copper pattern was also suggested. The change of the electrical resistance was measured during the bending fatigue test. It was found that the copper pattern containing 3wt% silane coupling agent exhibited the highest adhesion strength (5B) and lowest resistivity 24.5 μΩ?cm).