Abstract: THE INFLUENCE OF RADIOACTIVE SOURCE DECAY ON ISOTOPE INSTRUMENTAL ERRORMin Hainian;Yang Shiqing;Deng Congjun; Wang Jingmin(Institute of Isotope,the Academy of Sciences of Henan Province,Zhengzhou 450052)Abstract:The influence of radioactive source decay on measuring error of the isotope instruments is analysed.The valuable conclusion for designing the circuit of instrument is obtained.Keywords:radioactive source decay isotope instrument measuring error