The invention discloses a method for determining the content of chloramphenicol based on a biosensor of a glucometer, which comprises the following steps: connecting a specific complementary chain DNA sequence to the surface of a magnetic particle through biotin-avidin interaction, and releasing the specific DNA sequence through the specific action of chloramphenicol and an aptamer, and initiating a cyclic self-assembly process of a hairpin structure modified with gold nanoparticles/amylase, and measuring the content of chloramphenicol by utilizing magnetic separation and collection and combining with a glucometer. The preparation method comprises the following specific steps: S1, synthesizing AuNPs; S2, synthesizing aminated magnetic particles (MNPs); S3, modifying the MNPs (MNPs/tDNA/Aptamer); S4, carrying out DNA hairpin pretreatment (H1 and H2); S5, marking the NDA and glucoamylase (AuNPs/H1/E, AuNPs/H2/E) by using the AuNPs; S6, measuring chloramphenicol based on a glucometer; and S7, selectively investigating the content of chloramphenicol based on a glucometer. According to the method, the problem of measuring the content of chloramphenicol by using a glucometer is solved, and the detection requirement of the public on chloramphenicol is met.