This study was conducted to determine the effect of feed additives including probiotics, moisture and feed ingredients and the effect of fermented feed on digestibility and volatile fatty acid (VFA) level in finishing pigs. Feed was mixed with microbials including Saccharomyces, Lactobacillus, Enterococcus and Pediococcus together with different levels of probiotics, 0.25, 0.5, 1, 2, 3%. Addition of probiotics showed improved fermentation rate after 48 h incubation. To determine the optimal moisture level for fermentation, different levels of water, 30, 40, 50 and 60%, were added into the feed. Fermentation rate of feed with 40~50% moisture level was higher than that from 60% level at 60 h post-fermentation. In vitro fermentation rate of feed ingredients was analyzed by comparing VFA levels. Beet pulp and tapioca showed higher fermentation rate compare to other ingredients including canola meal or rapeseed meal. To determine the effect of administration of fermented feed In vivo, feces from finishing pigs were analyzed. Finishing pigs administrated with fermented feed showed improved digestibility and higher volatile fatty acid (VFA) level. In conclusion, results from the current study indicate that 40~50% of moisture with addition of beet pulp and tapioca in feed is optimal condition for fermentation. Furthermore, our data suggest that fermentation of feed can improve the feed quality and digestibility, thereby provide more nutrient in finishing pigs.