Abstract: The changes of solubility and immunoreactivity properties of Arah1, the main allergenic protein in peanut, were studied by immunological methods. The results showed that: Autoclaved treatment could significantly denaturate and decompose Ara h1 and peanut protein extracts, especially at 135 ℃; however, Ara h1 showed good thermal stability after 20 min treatment at 121 and 135 ℃, and the soluble protein content did not decrease significantly with the extension of treatment time; after being treated at 135 ℃ for 20 min or longer, main components of decomposition products were those protein fragments with molecular weight of 15 kDa or less. Autoclaving could significantly decrease the immunoreactivity of Ara h1, especially in the mixed system of protein extracts: After being treated at 135 ℃ for 20 and 60 min, the IgG immunoreactivity of Ara h1 was only 1/3 and 1/6 of that of control, respectively; in the mixed system, the IgG immunoreactivity of Ara h1 was only 2/9 and 1/9 of that of control under the same conditions.