Ara h 2 is one of the major allergen in peanut. Raw peanut was subjected to a series of sequential treatments, such as protein extraction, DEAE-Sepharose Fast Flow anion-exchange chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS—PAGE) recovery. The purified protein was identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI—TOF/MS). The results showed that the highly purified protein could be obtained by this method and was identified as Ara h 2 by MALDI—TOF/MS. The molecular weights of two constituents were 18.5 kD (Ara h 2.01) and 20.1 kD (Ara h 2.02). Recovery rate of column chromatography separation and SDS—PAGE electrophoresis were 31.4% and 18.6%, respectively.