Abstract: Based on“Method for Determination of Aluminium and Silicon in Fuel Oil”, SH/T 0706-2001，an aqueous solution of sample was prepared from pyrolysis tar by high temperature melting method and then the content of aluminium and silicon in the solution was determined by nitrous oxide-acetylene flame atomic absorption spectrometry at spectral wavelengths of Si 251.6nm and Al 309.3nm, respectively. The interference and elimination of coexisting Si and Al elements on spectral lines are discussed. The results proves that addition of citric acid and lanthanum nitrate can eliminate the chemical interference with Al measurement from Si，and cesium chloride can remove the interference with Al determination from Al ionization. Precision and accuracy tests show that the relative standard deviation for each of the two elements is less than 5％，and the adding standard recovery is 97.6％to 102.4％.

Key words: atomic absorption spectrometry, high temperature melting, pyrolysis tar, silicon, aluminium