Abstract: The synthesis of a new chromogenic reagent 2-(4-antipyrinylazo)-5-aminobenzoic acid(AAAB) is described.A selective spectrophotometry of palladium with AAAB is developed.In the presence of Tween 20,the palladium forms a red complex with AAAB in molar ratio 1:2 and its maximum absorption of is at 480nm.The molar absorptivity is 1.91×104L·mol-1·cm-1.Beer’s law is obeyed over the range of 0～25μg/25mL,and shows good selectivity.The method has been applied to the determination of microamounts of palladium in catalysts or slag containing palladium without special seperation.The proposed method is simple,rapid and accurate.