Abstract: HPLC was applied to the determinations of the main oxidation and intermediate products of mesitylene,including trimesic acid,mesitylenic acid and 5-methyl-1,3-benzenedicarboxylic acid.The conditions for separation and determination by HPLC were tested and optimized.The SHIMADZU C18 column (150 mm×4.6 mm,5 μm) was used as stationary phase,and a mixed solution of methanol,water and pH 5.0 acetate buffer solution (mixed in the a ratio of 79 to 20 to 1) was used as mobile phase.UV-detection at 225 nm was adopted in the determination.Linear relationships between the values of peak area and mass concentration of mesitylene,trimesic acid,mesitylenic acid and 5-methyl-1,3-benzenedicarboxylic acid in definite ranges were obtained.The values of recovery found by standard addition method were in ranges of 99.5%-100.4%,99.7%-100.8%,99.6%-100.8% and 99.3%-101.0% respectively.The values of RSD′s (n=6) were less than 2.0%.