Abstract: DC-Arc AES equipped with multi-channel optical detector-charge coupled device was developed for the determination of silicon in niobium and tantalum. The analytical spectral line of 288.160 nm was chosen for the determination of silicon. The buffering agent for silicon in niobium was the mixture of carbon dust and silver chloride,while for silicon in tantalum only carbon dust was used. Linear relationship between the spectral intensity and the mass fraction of silicon was obtained in the range of 0.001%-0.100% with correlation coefficients above 0.999 6. Recovery rates measured by standard addition method were in the range of 97.7%-103%,with RSD (n=7) less than 8%.