Abstract: In recent years, contamination of mineral oil hydrocarbons (MOH) in milk powder, especially infant formula, has become a public concern, and related international regulation has gradually escalated. However, there is no standard method for the determination of MOH in milk powder. In this paper, the sample pretreatment method based on the EU limits and analytical requirements were improved and optimized, and the saponification method, hexane extraction, silica gel clean-up, epoxidation reaction method in order were used, and a highly sensitive method for the determination of mineral oils of saturated hydrocarbons (MOSH) and mineral oils of aromatic hydrocarbons (MOAH) in milk powder by on-line high performance liquid chromatography-gas chromatography (HPLC-GC) were established. Results showed that, the method achieved a limit of quantification (LOQ) of 0.5 mg/kg and recoveries of 81.1%~112.0% (RSD=0.3%~3.8%), meeting the method requirements of the European Joint Research Center (JRC). The method was applied to analyze the international proficiency testing samples, and the results showed the detection results of MOSH and MOAH from C₁₆ to C₂₅ and C₂₅ to C₃₅ were close to the true values, and the absolute values of their z'-scores were less than 2. This indicated that the method passed the validation, and the method could be referred to as the standard for the determination of MOSH and MOAH in milk powder.