Gallic aldehyde was heated up by thermogravimetry from room temperature to 700 ℃ at different heating rates（5，10，15， 20 ℃/min） under nitrogen atmosphere while its DSC curve was obtained by differential scanning calorimetry at 10 ℃/min.The thermal decomposition mechanism was inferred in accordance with its weight loss and molecular structure while kinetic parameters in thermal equilibrium and original reaction conditions were calculated by double extrapolated method.Experimental results showed that after the volatilization of unbound and bound water，one molecule CO was lost due to the cracking of the aldehyde group.The decomposition reaction of gallic aldehyde was pushed to high temperatures with the increase of heating rates，and the maximum weight loss rate decreased in turn.The activation energy（Eα） of pyrolysis was 286.21 kJ/mol while pre-exponential factor（lnA） was 70.21.The pyrolysis mechanism function was g（α）=［-ln（1-α）］2/3 with reaction order（n） of 2/3.Pyrolysis activation energy decreased with the increase of conversion ratio.According to its kinetic parameters，the shelflives of gallic aldehyde was 4-5 years at room temperature.