Aims: The growth and metabolic activity of Aspergillus oryzae KKB4 in AFB1-contaminated corn and later coincided with AFB1 reduction and detoxification were investigated. Methodology and results: The decreasing of AFB1 amount by A. oryzae KKB4 could be clearly observed if the initial AFB1 concentration in corn was increased. Thus, moist-heated corn was artificially inoculated with Aspergillus flavus FNCC 62C7 to increase AFB1 content. AFB1-contaminated corn was applied as solid substrate and then inoculated with A. oryzae KKB4. During fermentation periods, the growth, metabolic activity, and AFB1 decline were investigated by glucosamine content, water content loss, and AFB1 concentration, respectively. The maximum growth was occurred in 4 thday at 1.499 ± 0.028 g glucosamine/ 100 g dry matter. The metabolic activity was going on up to the end of fermentation days, as shown as water content loss at 0.175 ± 0.007 g/g dry matter. In accordance with the growth and metabolic activity, the amount of AFB1 reduction was 37.04 ng AFB1/g dry matter during 5 days fermentation. According to toxicity analysis, it was found that the residues of AFB1 were not toxic to Bacillus megaterium cells. Conclusion, significance and impact of study: A. oryzae KKB4 is able to be applied in solid substrates as AFB1 reduction and detoxification agent. These lucrative effects are also important in relation with food and feed safety.