The concentration of trace rare earth elements (REEs) in breeding feed samples, which were collected from the experimentally in vivo tests with the poultry and fish was determined by using ICP-MS under the identical conditions. 115In internal standard was used for the measurement on ICP-MS in order to eliminate of the sample matrix effect. The fine ground samples were ashed at about 650oC in a stove and digested in a mixture of HNO3 and H2O2 on the hot plate, then followed by the evaporation until the moist residue obtained. The residue was dissolved in 2% (v/v) HNO3 for ICP-MS measurement. The analytical results from raw material of feeding products showed that the average value of total rare earth elements ΣREE content was within 3 to 5 g/kg, meeting the product quality requirements. The analytical procedure has been validated through the addition of rare earth standards into a commercial sample and via a standard reference material (SRM), which have shown the good agreement with detection limits of the method (MDL). It can thus be applied to the analysis of trace rare earth elements in breeding feed samples. This isthe first study to aim at establishing a standard procedure (SOP) to analyze the individual REEs traces in breeding feed for supporting the application of the organic REEs compounds in agriculture.