The invention discloses a protective fence for a highway and a mounting method thereof, whichrelate to the technical field of protective fences. The protective fence comprises two supports and a connecting mechanism, sliding seats are fixedly installed at the bottom ends of the two supports, an upper cross beam, a lower cross beam and a warning buffer mechanism are fixedly installed between the two supports, a solar cell panel is fixedly installed at the top of the upper cross beam, a distance sensor is fixedly installed at the front end of the left support, and an alarm is fixedly installed at the front end of the right support. The distance between a vehicle and the protective fencecan be monitored in real time through the distance sensor, and when the warning range is reached, a drivercan be reminded to keep a safe distance. And when the possible collision range is reached, the air bag is controlled to pop up, so that the impact force onthe vehicle is buffered, the deformation quantity of the collision vehicle can be effectively reduced, the recoil force caused by collision is minimized, secondary damage caused by the fact that the vehicle rushes out of the fenceis avoided, thecollision force in the vehicle during a traffic accident is reduced, and the safety of personnel in the vehicle is protected.