A method has been developed for the determination of trace impurities in silicon nitride (Si3N4) powders by fluorination assisted electrothermal vaporization (ETV)/ICP-AES using the slurry sampling technique. Polytetrafluoroethylene (PTFE) emulsion as a fluorinating reagent not only effectively destroys the skeleton of Si3N4, but also carries out selective volatilization between the impurity elements (Cu, Cr) and the matrix (Si). The experimental parameters influencing fluorination reactions were optimized. The detection limits for Cu and Cr are 1.05ng/mL (Cu) and 1.58ng/mL (Cr), the RSDs are in the range of 1.9-4.2%. The proposed method has been applied to the determination of Cu and Cr in Si3N4 ceramic powders. The analytical results were compared with those obtained by independent methods.