A novel series of 5-methyl-2-phenylphenanthridium derivatives were displayed outstanding activity against a panel of antibiotic-sensitive and -resistant bacteria strains compared with their precursor sanguinarine, ciprofloxacin and oxacillin sodium. Compounds 7 l, 7m and 7n were found to display the most effective activity against five sensitive strains (0.06-2 μg/mL) and three resistant strains (0.25-4 μg/mL). The kinetic profiles indicated that compound 7l possessed the strongest bactericidal effect on S. aureus ATCC25923, with the MBC value of 16 μg/mL. The cell morphology and the FtsZ polymerization assays indicated that these compounds inhibited the bacterial proliferation by interfering the function of bacterial FtsZ. The SARs showed that all the 4-methyl-substituted 5-methyl-2-phenylphenanthridium subseries could be further investigated as the FtsZ-targeting antibacterial agents.