An aflatoxin M1 nanobody, an immunosorbent and an immunoaffinity column. The aflatoxin M1 nanobody 2014AFM-G2 has the amino acid sequence of SEQ ID NO:7, is encoded by the nucleic acid sequence of SEQ ID NO:8, has a 50% inhibiting concentration IC50 to aflatoxin M1 of 0.208 ng/mL, and has cross reaction rates with aflatoxins B1, B2, G1, and G2 of 9.43%, 5.93%, 4.87% and 6.17%, respectively. The immunosorbent includes a solid phase carrier and aflatoxin M1 nanobody 2014AFM-G2 coupled with the solid phase carrier. The immunoaffinity column is loaded with the aflatoxin M1 nanobody immunosorbent. It can be used for purifying and concentrating an extracting solution of a sample before loading to a machine for detection and the immunoaffinity column can be used repeatedly for many times.