The BMPPT (4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione) was synthesized from BMPP. Its m.p. is 106-108℃. The results of the element analysis are as follows: C, 68.51%, H, 4.51%, N, 9.26%, S, 11.47%, which are in conformity with the theoretical value (C, 69.15%, H, 4.76%, N, 9.52%, S, 10.90%). The solvent extraction of Th⁴⁺ from nitric acid solution by BMPPT in benzene was studied. The extraction ability of BMPPT is not so high as that of its parent (BMPP). The Th⁴⁺ distribution ratio (D_Th) increases with the increasing pH of the aqueous phase, and pH_1/2 for Th⁴⁺was 3.2 ([BMPPT]=0.10 mol/L). When the pH increases, the distribution ratio of Th⁴⁺ increases linearly with the slope of 1.59. When the concentration of BMPPT increases, the distribution ratio of Th⁴⁺ increases rapidly. The lgD_Th-lg[BMPPT] is linear with the slope of 1.42 and the extraction mechanism is the cation ion-exchange.