We previously reported potent hit compound 4 inhibiting the wild-type influenza A virus A/HK/68 (H3N2) and A/M2-S31N mutant viruses A/WS/33 (H1N1), with its latter activity quite weak. To further increase its potency, a structure-activity relationship study of a series of imidazole-linked pinanamine derivatives was conducted by modifying the imidazole ring of this compound. Several compounds of this series inhibited the amantadine-sensitive virus at low micromolar concentrations. Among them, 33 was the most potent compound, which was identified as being active on an amantadine-sensitive virus through blocking of the viral M2 ion channel. Furthermore, 33 markedly inhibited the amantadine-resistant virus (IC50 = 3.4 μM) and its activity increased by almost 24-fold compared to initial compound, with its action mechanism being not M2 channel mediated.