Abstract: For the first time, an intriguing phenomenon was reported where diisopropyl azodicarboxylate (DIAD) transforms into diisopropyl hydrazine-1, 2-dicarboxylate (DIHD) during the gas chromatography (GC) analyzing process. Then a GC method with pre-column derivatization was developed and validated for the determination of residual DIAD. The triphenylphosphine (TPP) was used as derivatization reagent. The method was conducted on a gas chromatograph equipped with a flame ionization detector (FID), through direct injection, utilizing an Agilent HP-5 capillary column, and under programmed temperature conditions. The validation results indicated that DIAD exhibited a good linear relationship within the range of 1.057 µgmL^-1 ~ 10.57 µgmL^-1, with a detection limit of 0.528 µgmL^-1 and a quantification limit of 1.057 µgmL^-1. The established method can be used for the combined detection of DIAD and DIHD, which may be introduced during the manufacturing process. It has high accuracy and sensitivity, excellent repeatability and stability, as well as simple and rapid derivatization procedure. It is hoped that this method can serve as a general approach for the detection of DIAD and its structural analogues.