A method was developed for the determination of semicarbazide（SEM） by high performance liquid chromatography-tandem mass spectrometry（HPLC-MS/MS）.The degradation of azodicarbazide（ADA） to SEM under heat treatment was also studied.The method was optimized by using 2 nitrobenzaldehyde as derivative agent，at a derivative temperature of 37 ℃ and an extraction pH value of 70.The calibration curve was linear in the range of 05-100 μg·L-1 with a correlation coefficient（r） of 0999 and a detection limit of 04 μg·L-1The spiked recoveries at three spiked levels of 10，20 and 40 μg·L-1 were in the range of 996%-120%with relative standard deviations less than 7.6%.Results showed that ADA was degraded into SEM under heat treatment，and it was degraded completely at high temperature.Meanwhile，the formation rate of SEM increased with the increase of temperature，and it reached the maximum value of 0094% at 200 ℃.Nevertheless，the formation rate decreased with the decomposition of SEM when the temperature was exorbitant（>200 ℃）.Besides，it also decreased when the baking time lasted too long（>30 min）.