Bacteria capture and inactivation with multi-walled carbon nanotubes (MWCNTs) was investigated in this study. Raw MWCNTs (r-MWCNTs) was oxidized in mixed acid, yielding functionalized MWCNTs (f-MWCNTs) with carboxyl and hydroxyl group. UV-Vis absorption spectra and transmission electron microscope (TEM) shown that surface modifications led to elevated dispersity and stability of f-MWCNTs. The antimicrobial activities of f-MWCNTs to bacterial pathogen were further explored. Both the colony forming count method and OD growth assay demonstrated that individually dispersed f-MWCNTs showed a higher antibacterial activity compared to r-MWCNT aggregates, suggesting that dispersity of MWCNTs play an important role to antibacterial effect of CNTs. In addition, viability of bacterial cells treated with f-MWCNTs was found to be incubation time-dependent, however no correlation between incubation shaking speed and antibacterial activity of f-MWCNTs was observed. SEM and TEM prove that f-MWCNTs mostly wound around surfaces of cells instead of piecing into the bacterial cells. This is a convincing proof of physical sorption other than physical punctures, contributing to the possible antimicrobial mechanism of f-MWCNTs to bacterial cells.