Abstract: Plasma-enhanced chemical vapor deposition was used to prepare diamond-like carbon（DLC） film on the surface of TC4 alloy with different roughness. The composition, hydrophobicity, roughness and binding force of the films were characterized by Raman spectroscopy, contact angle meter, roughness meter and scratch meter, respectively. Meanwhile,the erosion corrosion behaviors of different DLC films were investigated by self-made erosion corrosion device. The effects of roughness on the erosion corrosion properties of DLC films on the surface of TC4 alloy were investigated, and the corresponding mechanism was also discussed. The results show that the increase in roughness can reduce the thermodynamic tendency of the film to corrode. The film with 800^# has the highest stability, which is not prone to corrosion. The erosion process is mainly affected by the bonding force between the film and the matrix. Adhesions of the films with the roughness of 60^# and 2000^# are lower, and the corrosive media penetrates through the damaged location easily in the process of erosion.This can result in the change of the hydrochemistry within the micro-zone and the corrosion increases. Finally, the film is failed under the synergistic effects of wear and corrosion.