The flexible printed electronics (e.g., wearable devices, roll-up displays, heating circuits, radio frequency identification (RFID) tags) calls for high-conductivity and low-cost materials, particularly for copper pastes. It is still a big challenge to develop reliable copper pastes for both antioxidant and high-conductivity flexible printed films and lines. In this work, an antioxidant copper paste was achieved using copper microflakes with surface passivation by formate ions and thiols, with high conductivity of 13400 S cm−1 (the same order of magnitude of silver pastes, 1.8–2.5 × 104 S cm−1). The universal applications of as-prepared copper paste in flexible printed electronics (e.g., electromagnetic interference (EMI) shielding films, anti-fog films, and RFID tags) via screen printing and curing at 170 °C under ambient atmosphere were demonstrated. The as-printed electronics showed high performance in flexibility, stability, and reliability. This work shows the great potential of anti-oxidation copper pastes in low-cost flexible printed electronics for commercial usage.