The work aims to improve the biocompatibility and antibacterial properties of titanium implants. Quaternary ammonium polyethyleneimide (QPEI) was grafted onto the surface of titanium by dopamine coating and surface initiated polymerization. The surface morphology, hydrophilicity, structure, antibacterial property, cytotoxicity, biocompatibility and an-ti-infection properties of the modified materials were evaluated by scanning electron microscopy (SEM), water contact angle test, X-ray photoelectron spectroscopy (XPS), confocal Laser Scanning Microscope (CLSM), cell experiments and animal experiments. The tertiary amine groups on polyethyleneimine (PEI) were successfully transformed into quaternary ammonium groups, and QPEI could be successfully grafted onto the implant surface by dopamine coating and surface initiated polymerization, but there were differences in antibacterial properties and cell compatibility. The antibacterial activity (inhibition efficiency = 89.69%) of the Ti-PGED-Q group with surface functionalized through surface initiation polymerization was significantly better than that of the Ti-PDA-Q group functionalized by dopamine self-polymerization. The surface initiation polymerization modification could affect early cell adhesion, but cell proliferation was not markedly affected. Moreover, Ti-PGED-Q did not induce obvious inflammatory reaction in vivo. When the material was planted in vivo for seven days, the surface inhibition efficiency was 85.4%, indicating the good in vivo antibacterial performance. The surface modifcation of the implant by surface initiated polymerization can improve the antibacterial performance and maintain good biocompatibility.