The present in vitro study was conducted to examine the effect of buffer solubility of eight protein feeds (coconut meal, distillers grain, sesame meal, perilla meal, soy source cake, rape seed meal, soybean meal and lupine) on the fermentation characteristics, degradability of dry matter (DM) and crude protein (CP), and methane (CH4) production by rumen microbes. Buffer extraction increased pH (P<0.05 ~ p<0.001) of the culture solution but tended to lower ammonia- N concentration for all protein feeds. Total volatile fatty acids(VFAs) and each VFAs concentrations in all incubation was decreased by buffer extraction (P<0.01 ~ P<0.001). Also, molar proportion of acetate in 1h (P<0.001), 3h (P<0.01) and 12h (P<0.05) incubations and molar proportion of propionate in 1h (P<0.001), 3h (P<0.01), 6h (P<0.05) and 12h (P<0.05) were decreased by buffer extraction. But molar proportion of butyrate in 1h (P<0.001), 3h (P<0.01) and 6h (P<0.05) were increased by buffer extraction. The in vitro effective degradability of dry matter (P<0.001) and CP (P<0.001) was decreased by buffer extraction. The methane production (P<0.01~P<0.001) in all incubation was decreased by buffer extraction. The results from in the current study might be useful for diet formulation to improve the feed efficiency of the ruminant animals without massive loss of major nutrients.