To clarify the antibacterial behavior at early adhesion, two titania nanotube (TNT) arrays were fabricated on polished commercially pure titanium (Ti), and the interaction mechanisms between TNT arrays and the model bacteria (Escherichia coli, E. coli) were investigated. The results show that TNT arrays exhibit a significant early antibacterial effect, which is highly related to the surface free energy and nano-topography. The underlying antibacterial mechanisms include: (1) the anti-initial-attachment effect at the lag phase (0-4 h); (2) the anti-proliferation and physical bactericidal effects at the logarithmic phase (4-12 h); (3) the reduced antimicrobial properties probably due to the overgrowth of bacteria on TNT arrays at the stationary phase (12 h and then).