The invention discloses an intelligent safe semitrailer comprising a semitrailer body, a plurality of wheels, a protection device and auxiliary safety devices. The protection device has triggering devices, a steel wire and a plurality of blocking devices, wherein the triggering devices are mounted on left and right sides of the lower part of the semitrailer body; each blocking device is installedon the external side of each wheel; one end of the steel wire is mounted on the triggering devices and the other end is mounted on the blocking device; when the triggering devices are triggered, the blocking devices are driven to work via the steel wire; and the auxiliary safety device is mounted on the left and right ends of the semitrailer body. the intelligent safe semitrailer is advantaged byrational structural design and convenient use; with the protection device mounted on the semitrailer and being isolated from the wheels, survival rate of a person upon accident can be improved; with the auxiliary safety devices mounted on the semitrailer body, a driver can be reminded of pedestrians upon a turn or the pedestrians can be separated from a vehicle, so vehicle safety can be enhanced.