A complexing agent, 2,3,4-trihydroxyacetophenoneoxime (THAPO) was prepared and developed a selective and sensitive kinetic direct spectrophotometric method for the determination of thorium(IV). The method sensitivity is calculated in terms of molar absorptivity (3.179 x104 L mo1-1 cm-1) and Sandell’s sensitivity (0.0073 μg cm-2), which explains that the method is more sensitive. The developed method is more precise and accuracy, which is found by standard deviation (0.0014), relative standard deviation(0.52%), absolute error(0.00057) and confidence limit(± 0.27). The metal and ligand forms 1:1(M:L) complex and its stability constant is calculated by Asumu’s and Edmonds and Birnbaum's method. This developed method was applied for the determination of thorium (IV) from thorite ore and checked the validity of the method by comparing the obtained results with AAS method.