Biomedical device-associated infections which engender severe threat to public health require feasible solutions. In this study, block copolymers consisting of antimicrobial, antifouling, and surface-tethering segments in one molecule are synthesized and grafted on polymeric substrates by a facile plasma/autoclave-assisted method. Hetero-bifunctional polyethylene glycol (PEG) with allyl and tosyl groups (APEG-OTs) is first prepared. PEGs with different molecular weights (1200 and 2400 Da) are employed. Polyhexamethylene guanidine (PHMG) which has excellent broad-spectrum antimicrobial activity and thermal/chemical stability, is conjugated with APEG-OTs to generate the block copolymer (APEG-PHMG). Allyl terminated PHMG (A-PHMG) without PEG segments is also synthesized by reacting PHMG with allyl glycidyl ether. The synthesized copolymers are thermal initiated by autoclaving and grafted on plasma pretreated silicone surface, forming permanently bonded bottlebrush-like coatings. Both A-PHMG and APEG1200/2400 -PHMG coatings exhibit potent antimicrobial activity against gram-positive/negative bacteria and fungus, whereas APEG1200/2400 -PHMG coatings show superior antifouling activity and long-term reusability to A-PHMG coating. APEG2400 -PHMG coating demonstrates the most effective in vitro antibiofilm and protein/platelet-resistant properties, as well as excellent hemo/biocompatibility. Furthermore, APEG2400 -PHMG greatly reduces the bacteria number with 5-log reduction in a rodent subcutaneous infection model. This rationally designed dual-functional antimicrobial and antifouling coating has great potential in combating biomedical devices/implant-associated infections.