An improved synthetic route of canthin-6-one was accomplished. To further enhance the antibacterial potency and improve water solubility, a series of 3-N-alkylated and 3-N-benzylated canthin-6-ones were designed and synthesized, and their in vitro antibacterial activities were evaluated. A clear structure-activity relationship with peak minimal inhibitory concentration (MIC) values of 0.98 (μg·mL(-)(1)) was investigated. Particularly, compounds 6i-r and 6t were found to be the most potent compounds with minimal inhibitory concentration (MIC) values lower than 1.95 (μg·mL(-)(1)) against Staphylococcus aureus.