Abstract: IC was applied to the determination of fluoride and chloride in silicon nitride after pyrohydrolysis. Sample of silicon nitride was pyrohydrolyzed at 1 050 ℃, and the volatile fluoride and chloride produced were absorbed by sodium hydroxide solution forming anions of F- and Cl- in solution, and determined by ion chromatography. 8.0 mmol·L-1 Na2CO3-1.0 mmol·L-1 NaHCO3 mixed solution was used as eluant, and restraining conductance detector was used in determination. Linearity ranges of F- and Cl- found were between 0.10-1.00 mg·L-1 and between 1.00-10.00 mg·L-1 with detection limits (3σ) of 0.017, 0.026 mg·L-1, respectively. The proposed method was applied to the analysis of silicon nitride sample, giving results in consistency with the values obtained by EDXRFS, and values of RSD′s (n=7) found were all less than 4.0%. Test for recovery was performed by standard addition method, giving values of recovery in the range of 84.5%-106%.