To improve the antibacterial properties of medical polyvinyl chloride (PVC), atmospheric pressure plasma jet (APPJ) technology was used to graft and prepare quaternary ammonium compounds (QAC) coatings on the PVC surface. The flow state and active components of the plasma jet were diagnosed by ripple shadowing and emission spectroscopy, respectively. The hydrophilicity, microscopic morphology and chemical components of the PVC surface before and after plasma treatment were characterized by static water contact angle method, scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The antibacterial performance of QAC/PVC against Escherichia coli was also tested. The results showed that with the increase of discharge voltage, the plasma jet flow state in the area of contact with PVC changed from laminar to turbulent flow. After plasma modification, the hydrophilicity of the PVC surface was enhanced. The water contact angle of the modified PVC surface could be as low as 26°, and the content of oxygen-containing functional groups was as high as 31.02 at%. The increase of discharge voltage contributes to the enhancement of the amount of oxygen-containing functional groups on the PVC surface and promotes the grafting and polymerization of quaternary amines on the PVC surface to form a dense coating, which improves its antibacterial performance against E. coli. [ABSTRACT FROM AUTHOR]