A new method suitable for determining specific activity of 230Th in uranium ore samples is built. The method is characterized by adding the 230Th/ 232Th standard dilution agent with lower activity ratio (Its 230Th/ 232Th activity ratio and Th have been known) to the samples and using isotopic dilution analysis. The method can be applied to analyses of 230Th specific activity in various 230Th/ 232Th activity ratio samples. The precision can also be improved. The method is characterized by adding the 230Th / 232Th standard dilution agent with lower activity ratio (Its 230Th / 232Th activity ratio and Th have been known) to the samples and using isotopic dilution analysis. The method can be applied to analyzes of 230Th specific activity in various 230Th / 232Th activity ratio samples.