4-(4,6-Dimethoxyl-pyrimidin-2-yl)-3-thiourea carboxylic acid ethyl ester was synthesized by the reaction of 2-amino-4,6-dimethoxyl pyrimidine, potassium thiocyanate and methyl chloroformate in ethyl acetate. Single crystals suitable for X-ray measurement were obtained by recrystallization with the solvent of dimethyl formamide at room temperature. The crystal structure was determined by X-ray diffraction analysis. Crystallographic data: C10H14N4O4S, M-r = 286.31, monoclinic, space group C2/c with a = 2.5309(3), b = 0.67682(6), c = 1.74237(19) nm, beta = 114.744(3)degrees, V = 2.7106(5) nm(3), D-c = 1.403 g/cm(3), mu = 0.225 mm(-1), F(000) = 1200, Z = 8, R = 0.0514 and wR = 0.1529.