Synthesis of 2-(4-oxoquinazolin-3(4H)-yl) acetohydrazide 3 was accomplished by the reaction of quinazolin-4(3H)-one 1 with ethyl bromoacetate followed by treatment with hydrazine hydrate. The key starting materials 3 was used for synthesis of the target 2-(3-acetyl-2, 3-dihydro-5-[(4-oxoquinazolin-3(4H)-yl)-methyl]-1, 3, 4-oxadiazol-2-yl) phenyl acetate 5. Thus, the reaction of 3 with salicylaldehyde afforded N'-(2-hydroxybenzylidene)-2-(4-oxoquinazolin-3(4H)-yl) acetohydrazide 4. Cyclization of 4 with acetic anhydride leading to the formation of 2-(3-acetyl-2, 3-dihydro-5-[(4-oxoquinazolin-3(4H)-yl) methyl]-1, 3, 4-oxa-diazol-2-yl) phenyl acetate 5. The structure of 2-(3-acetyl-2, 3-dihydro-5-[(4-oxoquinazolin-3(4H)-yl) methyl]-1, 3, 4-oxadiazol-2-yl) phenyl acetate 5 was established by elemental analysis, infrared, mass spectra, and nuclear magnetic resonance. Also, anti-tumor estimation of the new compounds in vitro through three cell lines HepG2 (liver carcinoma), HCT-116 (colon carcinoma), and MCF-7 (breast carcinoma) revealed that they own high anti-tumor activities.