A polypropylene-grafted poly(hexamethylene guanidine) (PP-g-PHMG)/polyethylene (PE) monofilament was prepared by melt blending and spinning using PE and PP-g-PHMG. The effect of PP-g-PHMG content on the structure, mechanical properties, and antimicrobial properties of PP-g-PHMG/PE alloy monofilaments was studied. Compared with PP/PE without grafting PHMG, T m of PP-g-PHMG/PE alloy monofilaments increased due to rigidity of PHMG grafted. In the PP-g-PHMG/PE alloy monofilaments, the total degree of crystallinity of alloy monofilaments decreased; hence, the α -relaxation associated with the crystalline region of the polymer matrix becomes weaker as PP-g-PHMG content increases. The breaking strength of PP-g-PHMG/PE alloy monofilaments decreased while the knotting strength increased by increasing PP-g-PHMG content. The antibacterial test showed that the PP-g-PHMG/PE alloy monofilament had obvious inhibitory effect on E. coli and Staphylococcus aureus . Therefore, the PP-g-PHMG/PE alloy monofilament has the potential to make green and highly effective antifouling materials.