This study was carried out to determine the adequate levels of alkaline hydrogen peroxide treatment for the improvement of nutritive value of rice straw. In vitro digestibility and chemical analysis after several treatments were measured. Treatment variables were soaking time(12, 24, 48 and 96 hrs), temperature(5, 25, 50 and 75℃) of alkaline H₂0₂ solution, H₂0₂ concentration (0.5, 1, 2, 3 and 4%) and substrate /solution ratio (1, 2, 3, 4 and 5g/ml). The results obtained were summarized as follows. 1. The DM digestibilities or rice straw treated with H₂O₂ for 24 and 48 hours were higher than those of the others(p$lt;0.05). There was no differ ences when the rice straw was treated for 12, 72 or 96 hours. Cell wall contents were not affected by the time of treatment. 2. The DM digestibilities were higher at pH 11.5 or above(p$lt;0.05) and was decreased as pH declined. When rice straw was treated with H₂O₂ at pH 11.5 or higher, NDF, ADF and cellulose contents were increased. However, lignin content and DM recovery percentages were decreased. 3. The DM digestibilities were not influenced by the ratio of straw versus liquid. The contents of NDF and cellulose were not affected up to the ratio of 4g rice straw/50m1, but were decreased at 5g rice straw/50m1. Lignin content and DM recovery percentages, however, were increased at 5g rice straw /50m1. 4. The DM digestibilities were not different among treatments at 5, 25 and 50℃. However, the rice straw treated at 75℃ showed lowest digestibility of all treatment (p$lt;0.05). The content of NDF, ADF and cellulose was increased by increasing temperature. However, lignin content and DM recovery percentages were decreased by increasing temperature. 5. The AHP treated rice straw had higher content of ADF and cellulose, and lower content of hemicellulose and lignin as the concentration of H₂O₂, increased. But hemicellulose, lignin and DM recovery percentages were decreased. The NDF content was not different among five different concentrations of H₂0₂ solution. In conculsion, based upon the results of present experiments the most desirable method is to soak rice straw in 1% alkaline H₂0₂ solution at pH 11.5, at room temperatrve (25℃), for 24∼48 hours and at the ratio of 4g rice straw /50m1 solmtion.