Rapid detection as an efficient and convenient detection method is considered to be an important means to effectively improve food safety detection and clinical diagnosis capabilities. Magnetic relaxation switching (MRS) biosensor has become a new method and new tool for rapid detection due to its excellent analytical performance and simple analysis process. The development of MRS biosensor began with the discovery of magnetic relaxation. When the state (dispersion or aggregation) of superparamagnetic nanoparticles changes in aqueous solution,the uniformity of its local magnetic field can be changed to form a nonuniform local magnetic field followed by a transverse relaxation speed acceleration of the surrounding water molecules and shortening of the transverse relaxation time. Based on this principle,different biomolecular recognition elements including antibody,enzyme,nucleic acid can be used to assemble MRS biosensor for rapid detection of targets. MRS biosensors can be mainly classified into four types: (1) Magnetic nanoparticles-mediated MRS biosensors,which contain the MRS biosensors based on the state change of magnetic nanoparticles; (2) MRS biosensors based on the number change of magnetic nanoparticles ; (3) MRS biosensors based on the state and number changes of magnetic nanoparticles; (4) Paramagnetic ion mediated MRS biosensors,a novel MRS biosensors based on the spatial dipoledipole interactions between paramagnetic ions (contain multiunpaired electrons) and hydrogen protons. Combined with portable miniature NMR instrument,MRS biosensors can be realized on site quick testing. In this paper,we reviewed the different sensing principles and the progresses of MRS. In addition,we discussed the development and improvement of MRS in the aspects of signal transformation mechanism,the performance of magnetic probe,signal amplification system and biosensor stability. Finally,we discussed the main problems of MRS biosensors. The future development or breakthrough of MRS biosensors in the field of rapid detection was prospected.