The early warning is significant forpreventing stored maize from aflatoxin B₁ (AFB₁) contamination. To reveal the relationship between the change of catalase activity and AFB₁ contamination in stored maize, the storage experiments of maize were carried out at different temperatures and moisture contents. The results showed the increasing trend of catalase activity and contaminated AFB₁ was accordant, which displayed a quadratic equation with the correlation coefficient of more than 0.95. The rates of catalase activity increase and AFB₁ production by mould in maize could be affected by storage temperature and maize moisture content, but their increasing trend was not changed. Moreover, it was found that catalase activity increase 4 to 21 days before the significant increase of AFB₁ content under each maize storage condition. Therefore, the early warning of AFB₁ contamination in stored maize could be achieved by the detection of catalase activity of mould in stored maize.