In order to study the loosening behavior of bolted structures in high temperature environment,the research about the loosening behavior and protection methods of bolted structures was carried out under the coupling action of temperature and lateral vibration loads.After experiments,the damage morphology of the thread surface was analyzed to reveal the wear mechanism by using optical microscope,white light interference three-dimensional topography instrument and scanning electron microscope.The loosening behavior of the bolted connection structure was studied by the dynamic response method.The test results show that with the increase of temperature,the relative motion between the contact surfaces gets serious because of the inconsistent thermal deformation of the bolted connection structure.Under the same lateral alternating displacement load,the wear of the bolt surface is more serious,and the looseness of the bolted connection structure increases.At room temperature,the connection structure of DLC coated bolt/nut and CrAlN coated bolt/nut connection structure has a good anti-loosening performance.