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Cu-bearing antibacterial martensitic stainless steel (MSS) has a broad application prospect in cutting field, which needs a combination of good antibacterial property and high hardness. In this work, 420Cu stainless steel (SS) with high Cu addition and different austenitizing temperatures were investigated to address the above issue. The results of plate count measurement and biofilm observation indicated that 420Cu SS austenitized at lower temperature shows better antibacterial performance. The Rockwell hardness was up to 52.7 HRC and corrosion resistance evaluated by electrochemical polarization was also acceptable. Scanning electron microscope (SEM) observation further revealed that the treated 420Cu SS possessed of the martensitic microstructure with more undissolved carbides and Cu-rich precipitations, which led to the higher hardness. Mott-Schottky and inductively coupled plasma-mass spectrometry (ICP-MS) tests implied that above precipitations decrease the compactness of passive film and then promote the release of Cu ions, which ensured the 420Cu SS good antibacterial property. [ABSTRACT FROM AUTHOR]