The invention relates to the technical field of constructional engineering, and discloses a safety auxiliary device for unloading of a dump truck, which comprises a rotating shaft. A rotating disc is fixedly connected to the outside of the rotating shaft, a first shell is fixedly connected to the inside of the rotating disc, a stop lever is movably connected to the inside of the first shell, and a shell is movably connected to the outside of the rotating shaft. The interior of the shell is fixedly connected with a fixing ring, the interior of the fixing ring is fixedly connected with a coil, the interior of the shell is fixedly connected with a second shell, and the interior of the second shell is provided with an electrorheological body. Through the interaction of the rotating shaft, the rotating disc, the first shell, the stop lever, the support, the photosensitive assembly and the alarm, when the vehicle unloads, if the vehicle suddenly moves forwards, an alarm can be given to remind surrounding personnel to pay attention to safety, meanwhile, a driver is reminded to control the vehicle, and when the vehicle runs normally, the device structure does not affect normal rotation of the rotating shaft, and therefore, the driving of the vehicle is not influenced.