Abstarct: 3,4 – dihydropyrimidine -2-(1H)-ones are compounds which exhibit medicinal and biological activities. In this research we have synthesized several compounds via Biginelli reaction by using 1- butyl -3- methyl imidazolium bromide [BMIm]Br ionic liquid as a new catalyst. This catalyst has been already reported to be benign to environment. Condensation of ethyl acetoacetate with urea and aromatic aldehydes at 100 ℃ in the presence of 1- butyl -3- methyl imidazolium bromide [BMIm]Br ionic liquid give rise to 3,4 – dihydropyrimidine -2-(1H)-ones derivatives which can have substituents at position 2, 4, 5, 6 of the ring. Structures of the products are confirmed by spectroscopic data. As special features of the reaction one can point to high yields, short reaction time, one-pot and solvent free reaction, without any need to separate the intermediates and finally use of benign catalyst to environment.