This experiment was conducted to determine the effect of ammonia treated rice straw on nutritive value and rumen characteristics. Rice straw was treated with aqueous NH₄OH to supply 40g NH₃ Kg^(-1) straw dry matter. The reaction time with ammonia was 6 weeks at room temperature. The results are as follows: Crude protein content increased more than 2 times by treatment, and the NDF content was decreased about 4.7%. The effect of ammoniation was the important factor in enhancing IVDMD. Ammoniation resulted in the significant improvements in intake, digestbility and nutritional quality. Improvements in nitrogen and sulfur retention was significant with treated straw. Also, Molar proportions of acetate increased (P$lt;.01) and butyrate decreased (P$lt;.01) with ammoniation. In conclusion, ammoniation is a simple and effective method of improving the feeding value of rice straw.