The present study demonstrates the simple and easy synthesis of calcium oxide (CaO) from waste egg’s shells. Fine egg’s shells powder were calcinated at 500, 700 and 800 ºC. The structural and morphological evaluation of calcium oxide derived from waste egg’s shell were examined by using XRD, FT-IR, SEM, EDS and TEM techniques. The sintered calcium oxide was used as heterogeneous catalyst for the synthesis of 5-arylidene malononitrile and 5-arylidene barbituric acid derivatives by the condensation of various aromatic aldehyde and active methylene compounds via Knoevenagel condensations reaction under ultrasound irradiation method. The reaction completed within a very short reaction time with high yields of product. The present method describes easy synthesis of calcium oxide catalyst from the waste egg’s shells, short reaction times, simple product isolation, excellent yield and reusability of the catalyst.