The invention relates to a catalyst for synthesis of allantoin by the reaction of glyoxylic acid and urea and a corresponding reaction process. The catalyst is the solid acid catalyst and takes one or the combination of more of oxides and molecular sieves of IVB to VIB elements as a carrier, or a complex which is composed of one or the combination of more of the oxides and the molecular sieves of IVB to VIB elements and one or the combination of more of the oxides of IB, IIB, VIIB, VIIIB and rare earth element as the carrier, and the carrier is carried out the impregnation supporting, the drying and the calcination by using inorganic strong acid or ammonium salt solution thereof for the preparation. The use of the catalyst can synthesize an allantoin product by one-step reaction of the glyoxylic acid and the urea in an atmospheric pressure tank reactor. The catalyst of the invention has the advantages of high activity and stability, recyclable property, no corrosion of the device and environmental pollution, etc. The synthesis reaction process of the allantoin has the advantages of simple process, less using amount of the catalyst, short reaction time and high yield of the allantoin, etc.