The invention relates to a full automatic both side straddle mounted type road guardrail which solves the problems of time consuming, great effort, low efficiency in the prior art during cleaning a road guardrail; the adopted technical proposal is as follows: the structure internally comprises a storage water tank, a box body, a motor power supply mechanism arranged in the box body, a driving motor, an actuating mechanism, a travelling mechanism, a cleaning mechanism, a water level sensing mechanism, and is provided with a self-navigation system matched with the traveling mechanism so as to control the steering of the device. The cleaner is internally provided with a water adsorption roller, a water touch roller and a scrubbing brush roller for completely cleaning the guardrail; the motor power supply mechanism is charged by a solar battery. The cleaner has simpler operation, convenient unloading, low cost, environmental protection, high working efficiency, and complete cleaning.