The invention relates to a method for detecting gentamicin through clinical magnetic resonance imaging, and belongs to the technical field of immunodetection. The method is to add standard gentamicin supernatant or gentamicin supernatant to be measured, gentamicin antibodies and goat-anti and rabbit-anti antibodies into gentamicin modified magnetic nano particles, and use the antibodies and the gentamicin modified magnetic nano particles to form immune polymers so as to generate magnetic resonance signals and perform magnetic resonance detection. The magnetic resonance signal detection method utilizes the antibodies and the gentamicin modified magnetic nano particles to form the immune polymers, and effectively shortens the transverse relaxation time T2 value of protons in water so as to generate signals. In general, when the concentration of the gentamicin in a sample is larger, the quantity of the gentamicin caught by the antibodies is more, the quantity of the antibodies which are combined with the gentamicin on the surface of the magnetic nano particles is fewer, and the measured T2 value is larger. The method does not need complex sample pretreatment, is simple and convenient to operate, only needs to add the sample to be measured for incubation and directly measure the T2 value, and can complete the process by one step. Moreover, the particle diameter of superparamagnetic nano particles for marking is approximately 10 nanometers, so that the water solubility is high and the dispersity and the stability are good.