This study was designed to determine the characteristics of rumen fermentation, and post-ruminal protein digestion of untreated and treated soybean meal (SBM) using gas production (GP) technique and three step in situ/in vitro procedures. Soybean meal (SBM) was treated by autoclaving, roasting, with ethanol and mixed by various proportions of  Acacia saligna (AS) leaves (1:3, 1:1, 3:1) ratios. The results showed that the highest cumulative GP was observed in untreated SBM followed by treated SBM with ethanol, roasted SBM and SBM+AS (3:1). The lowest mean values of GP were obtained in SBM+AS (1:3), autoclaved SBM and SBM+AS (1:1). The predicted metabolizable energy (ME, MJ/kg DM) and net energy (NE, MJ/kg DM) varied widely in substrates and was particularly high in untreated SBM, while SBM+AS (1:3) had significantly the lowest values of ME and NE. The highest mean values of NH₃-N concentration were obtained with untreated SBM, while the lowest was obtained with autoclaved SBMand followed by SBM+AS (1:3), ethanol-treated SBM and roasted SBM. Rumen degradable protein (RDP, %) varied from 33.6% in autoclaving SBM to 62.4% in SBM+AS (3:1). Intestinal protein digestion (IPD, %) content was highest in autoclaving-SBM, roasting SBM and untreated SBM and lowest mean value of IPD was recorded in SBM+AS (1:1).The highest mean values for VFA concentrations were obtained with SBM+AS (3:1)and SBM treated with ethanol followed by SBM plus A. saligna leaves (1:3). The lowest mean value of VFA concentration was obtained by autoclaving SBM or roasting SBM. It is concluded that autoclaving SBM, ethanol- treated SBM and mixing SBM with Acacia leaves (1:3) could be used advantageously to reduce RDP and increase the bypass protein but the autoclaving SBM showed the best treatment on improving the intestinal protein digestion of SBM.