A method of determining the content of hydrazodicarbonamide(HDC) in bread by high performance liquid chromatography in tandem atmospheric pressure chemical ionization source mass spectrometry (HPLC-APCI-MS) was established. Using 80 ℃ water as extractant, N-hexane extraction was used to remove sample impurities. And then the samples purified were separated by using Xbridge BEH Prep OBD Amide column. The gradient elution was performed by using wateracetonitrile (37) (v/v), with the flow velocity 0.6 mL/min. The ionization were achieved by using APCI source positive ion mode with MRM scan mode. The internal standard calibration curves were used for quantitative. The method of adding-recovery were used to test. The results showed good linearity in the range of 0.2～10.0 mg/L, and the correlation coefficient was 99.5%～99.9%. The indoor average recovery was between 82%～110% and the precision of the laboratory was less than 10.3%, which could satisfy the general requirement of analysis method. Moreover, the method is simple, rapid and sensitive, which is suitable for the determination of HDC in bread.