Abstract: This paper describes the measurement of isotopic abundance ratio ofcopper in leukemia blood and, for comparison, the normal blood and natural copper sample have also been measured. Silicon gel-H_3PO_4 was used asstabilizer to get higher sensitivity and more stable ion current. It is provedthat organic impurities in blood sample interfere the measurement of copperseriously. To obtain better precision baking the samples made from blood isnecessary. The results show that isotopic compositions of copper in leukemiablood are the same as those in normal blood and in natural copper sample.The precision is better than ±0.5% for blood measurement.