Abstract: With the aim of enhancing the toughness of epoxy based conductive ink, we adopted a vinylchoride-vinylacetate-dicarboxylic acid terpolymer (E15/45M) to toughen epoxy resin E51. Flexible conductive ink was prepared with 2-ethyl-4-methylimidazole (2E4MI) as curing agent and Cu@Ag powder as conductive filler. The results indicate that the volume resistivity of conductive ink decreases with the conductive filler content increasing. It also finds that the volume resistivity of conductive ink decreases firstly and then increases, as the content of 2E4MI increases. The optimal mass ratio of 2E4MI to E51 is 1:5, and with further investigation, the best curing temperature and time of conductive ink are 105 ℃ and 2.5 h, respectively. E15/45M can not only enhance the flexibility of conductive ink, but also decreases the volume resistivity. With increasing the content of E15/45M, the glass transition temperature of E15/45M/E51-2E4MI glue film decreases from 91.5 ℃ to 58.0 ℃, and the volume resistivity of conductive ink decreases from 27.5×10^-4 Ω·cm to 9.50×10^-4 Ω·cm. When mass ratio of E51-2E4MI to E15/45M is 50:50, the volume resistivity of the conductive ink with conductive filler content of 70wt% reaches 9.57×10^-4 Ω·cm, the adhesion grade is zero, and the resistance variation is less than 80% after folding repeatedly for 20 cycles. Therefore, toughening epoxy resin with E15/45M can improve both the flexibility and the conductivity of conductive ink.