A green and efficient method for the synthesis of (4 or 5)-aryl-2-aryloyl-(1H)-imidazoles via self-condensation reaction of arylglyoxal hydrates in the presence of ammonium acetate using water as solvent under ultrasonic irradiation was reported. The reactions proceeded in high yields and very short reaction time. Introduced procedure is completely ecofriendly and don’t need any toxic organic solvent in all performing steps. In addition, we use computational chemistry for acquiring some information about the thermochemistry and geometrical structure of these imidazole derivatives.