To evaluate the effect of NaOH treatment on peanut straw of the different parts, chemical composition, in vitro dry matter digestibility (IVDMD, %) and in vitro organic matter digestibility (IVOMD, %) were tested. The parts of peanut straw were devided into four parts of blade, stem, hull and whole straw. The results obtained are summarized as follows; 1. The blade contained more crude protein, crude fat, nitrogen free extract and crude ash, but reverse phenomina were observed in the contents of crude fiber and cell wall constituents than the others. 2. In vitro dry matter digestibilities (IVDMD, %) of the four parts of NaOH-treated peanut straw were highly significantly different (p$lt;0.01) in different levels of NaOH treatment and of in vitro times. 3. In vitro organic matter digestibilities (IVOMD, %) of the four parts of peanut straw were showed the same tendency with the IVDMD`s (%).