3,4-Dihydropyrimidin-2-(1H)-ones were synthesized in high yields by a one-pot cyclocondensation of aldehyde, 1,3-dicarbonyl compound, and urea or thiourea using copper o-toluenesulfonate as a catalyst under solvent-free conditions at 90℃. Effects of molar ratio of reactants,amount of catalyst,and reaction temperature on the yields of 3,4-dihydropyrimidin-2-(1H)-ones were investigated. The results showed that at the condition of n_(aldebyde):_(1,3-dicarbonyl compounds):n_(urea(or thiourea)) =1:1.2:1.5,1 mol% catalyst (molar percent of aldehyde) ,2.0 h at 90℃ ,the yields of products were 51-96%. After reaction,the catalyst could be reused for four times without distinct loss of catalytic activity.