To enhance the laboratory ability of quality control and method validation in the determination of natural occurring PCDD/Fs, dl-PCBs and their analoguesin milk, thereference material was prepared and certificated. MethodsThe milk samples were homogenized, packed and cryodesiccated, then the PCDD/Fs and dl-PCBs were analyzed by high resolution gas chromatography/high resolution mass spectrometry using isotope dilution and internal standard quantization techniques. Afterthe homogeneity and stabilitytest, the certification was conducted with 5 qualified laboratories. ResultsThe 10 bottles of milk samples were randomly selected and were tested for the cross-sample homogeneity, and PCDD/Fs and dl-PCBs in milk samples were homogeneous. The stabilities of the PCDD/Fs and dl-PCBs in milk samples were tested over one year at room temperature and the levels were stabilized.ConclusionThe natural reference material of PCDD/Fs and dl-PCBs in milk was first prepared and certificated and was intended to be used for quality control and method validation in the determination of PCDD/Fs, dl-PCBs and their analoguesin milk samples.