Abstract: Plastic has become a common material in our daily life. The influence of a plastic additive, decabromodiphenyl ether (BDE-209), on the environment and human health has gradually attracted worldwide attention. The pretreatment of complex matrix such as plastic is very important for accurate qualitative and quantitative analyses of target compounds. In this study, the extraction and analysis of the target BDE-209 in a matrix of polyethylene (PE) plastic Certified Reference Material (CRM) by using Agilent 1290 HPLC-DAD were carried out. By optimizing the pretreatments process, the problem of plastic dissolution and precipitation was solved, and the final sample solution could be detected and analyzed by using Agilent 1290 HPLC-DAD. Good accuracy and stability of the detection results were obtained. RSD was less than 3.9%. The LOD (S/N=3) and LOQ (S/N=10) of decabromodiphenyl ether were 0.017 μg·mL⁻¹ and 0.05 μg·mL⁻¹, respectively. The linear range of BDE-209 was 0.5 μg·mL⁻¹～50.0 μg·mL⁻¹ with R²=0.999. The method can be applied to quantitative analysis of CRM candidates such as polypropylene (PP) and acrylonitrile-butadiene-styrene (ABS).