The utility model discloses an install wheel protection device's semitrailer, automobile body, a plurality of wheel and protection device including the semitrailer, protection device includes that trigger device, steel wire and a plurality of shelter from the device, and trigger device installs in the left and right both sides of the lower part of automobile body, shelters from the device and allinstalls in the outside of wheel, and the one end of steel wire is installed on trigger device, and the other end of steel wire is installed on sheltering from the device, drives the device work of sheltering from through the steel wire when trigger device is triggered. The utility model has the advantages of structural design is reasonable, convenient to use, through trigger device, steel wire and the cooperation of sheltering from the device, protect the space in certain region of automobile lower body, the security that the vehicle travel has improved, still install the restorer on the trigger device simultaneously, do not need the manual work to reset, saved manpower and materials.