Abstract: Rare earth elements and thorium in RE-Nb-Ta ores were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The factors affecting the determination such as sample pretreatment method, sample dose were investigated. The determination wavelengths for target elements were selected and the working parameters of the instrument were optimized. The interference from the coexistent elements had been tested. The results showed that the interference among rare elements could be neglected. The accuracy and precision of the method were tested. The precision for all elements (except for Eu2O3) was less than 10%RSD(n=11). The results were in agreement with those provided by ICP-MS and other methods.