Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry（MALDI-TOF MS） was used to analyze the end-group distribution of poly（p-phenylene terephthalamide）（PPTA）.Samples were prepared by the evaporation-grinding（E-G） method.In order to improve the grinding of PPTA，the samples were treated with concentrated sulfuric acid until they became soft before the sample preparation.3-Aminoquinoline was employed as the matrix material with potassium trifluoroacetate as the cationizing agent.The ratio of matrix-to-polymer was optimized in order to achieve higher signal-to-noise ratio.The MALDI-TOF MS spectrum of the sample with residual sulfuric acid was compared with the MS spectra of the sample without residual sulfuric acid，the influence of residual traces of sulfuric acid on the MALDI-TOF MS spectra was analyzed.The results showed that a relatively higher signal-to-noise ratio was obtained at the matrix-to-polymer mixing ratio of 20∶1 in the reflection mode.The peak splitting from hydrogen/sodium and hydrogen/potassium exchange，the amino-group fragment loss and decarboxylation probability were also reduced by the residual traces of sulfuric acid in the samples，which could improve the signal-to-noise ratio and reliability.