In this study, 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (3a-3h) reacted with 3-benzenesulfonyloxy-4-methoxybenzaldehyde (1a-1h) to afford eight new 3-alkyl(aryl)-4-(3-benzenesulfonyloxy-4-methoxybenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (4a-4h). Then, the acetylation reactions of compounds 4a-e and 4g were investigated and compounds 5 were obtained, respectively. The structures of fourteen new compounds were characterized by elemental analysis, IR H-1 nuclear magnetic resonance (NMR), C-13 NMR, mass spectrometry, and ultraviolet spectral data. The synthesized compounds were analyzed for their in vitro potential antioxidant activities in three different methods. Compounds 4d, 4e, and 5g showed the best activity for iron binding. In addition, the compounds 4a-4h were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents. Furthermore, these 14 new compounds and 14 recently reported 3-alkyl(ary1)-4-(4-benzenesulfonyloxybenzylidenarnino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (6a, 6b, 6d, 6e, and 6g-6i) and 1-acetyl-3-alkyl(aryl)-4-(4-benzenesulfonyloxybenzylide 4,5-dihydro-1H-1,2,4-triazol-5-ones (7a, 7b, 7d, 7e and 7g-7i) were screened for their antimicrobial activities.