Abstract:A new synchronous fluorescence spectrophotometry method was developed for the determination of trace cephradine in animal food.The method was based on the condition that Cephradine was degradated in acidic condition and fluorescence intensity of its degradation product was increased by Twain-20.The degradation condition and wavelength difference（△λ）were selected.The effects of heating time，the volume of sulfuric acid，pH，the effect of type and amount of surface active agent on the fluorescence intensity of degradation product were discussed.The results showed：1.5 mL 2.0 mol/L sulfuric acid was selected，heating time was 120 min，the buffer of Na2CO3-NaHCO3was used to increasing pH to 10.6，1 mL 5%Twain-20 solution was added.The standard and sample solution were putted into 1cm fluorescence cuvette，Synchronous fluorescence spectrums were scaned from 420 nm to 550 nm，△λ was 90，the fluorescence intensities were readed at 468 nm. The protein in food sample were precipitaded by acetonitrile.In the range of 0.02 μg/mL-2.00 μg/mL，the concentration of cephradine and the fluorescence intensity of its degradation product had good linearity，the correlation coefficients was 0.999 2，the detection limit was 2.71 ng/mL.At spiked levels of 0.40 μg/mL to 0.60 μg/mL，the recoveries were 93.91%to 96.90%，the relative standard deviation was 0.50%to 0.90%（n=3）.The new method could be used for residue cephradine in animal food.