An immunoadsorbent for purifying fumonisin B1, aflatoxin B1, ochratoxin A, zearalenone and sterigmatocystin; a complex affinity column and its preparation method; and a method for detecting the mycotoxins using the same are provided. The immunoadsorbent comprises a solid-phase support, and an anti-fumonisin B1 monoclonal antibody, an anti-aflatoxin B1 monoclonal antibody, an anti-ochratoxin A monoclonal antibody, an anti-zearalenone monoclonal antibody and an anti-sterigmatocystin monoclonal antibody which are coupled to the solid-phase support, wherein the anti-fumonisin B1 monoclonal antibody is secreted by a hybridoma cell strain Fm7A11. The complex affinity column can be used for purification and detection of a fumonisin B1 sample, an aflatoxin B1 sample, an ochratoxin A sample, a zearalenone sample and a sterigmatocystin sample at the same time.