Abstract: Disease problems caused by bacterial infections have resulted in widespread concern worldwide. Although antibiotics can effectively treat bacterial infections, unreasonable use and abuse can cause bacteria to develop drug resistance. Therefore, it is particularly urgent to solve the problem of bacterial drug resistance and develop safe and efficient non-antibiotic antibacterial agents. We grafted epoxypropyl dodecyl dimethyl Ammonium chloride (DDEAC) the surface of biodegradable cyclic cross-linked poly (cyclotriphosphazene-co-polyethyleneimine) microspheres (PHP), and successfully prepared ring-crosslinked poly (cyclotriphosphazene-co-polyethyleneimine) grafted quaternary ammonium salt microspheres (PHPD). In addition, using FTIR, XPS, TG, TEM and FESEM to characterize and analyze the structure and morphology of the microspheres, and studying its antibacterial activity and cytotoxicity. The experimental results show that the modified antibacterial microsphere PHPD (50 μg/mL) has an antibacterial rate of 97.3% against E.coli and S.aureus. The material overcomes the high toxicity defect of using the quaternary ammonium salt DDEAC material alone, and achieves high-efficiency antibacterial while also has good cell compatibility. Therefore, this research has certain guiding significance for the development of safe and efficient nano-antibacterial agents.