The invention relates to a cleaning device, in particular to a rotary drilling rig blade cleaning device for construction machinery. The invention is to provide a rotary drilling rig blade cleaning device for construction machinery in which water resources cannot be wasted and water is not easily gotten onto a person. In order to solve the technical problem, the invention provides the rotary drilling rig blade cleaning device for construction machinery. The rotary drilling rig blade cleaning device for construction machinery comprises a bottom plate and the like, wherein a lifting device is arranged at the top of the bottom plate, and a cleaning device is arranged on the lifting device; a water tank is arranged on the cleaning device, and the right side of the bottom of the water tank is connected with a first water outlet pipe; a first valve is arranged on the first water outlet pipe. The cleaning device can be in tight contact with blades of a rotary drilling rig through the liftingdevice, so that the blades of the rotary drilling rig are positioned in the water tank; the blades of the rotary drilling rig can be flushed by the flushing device, so that the blades of the rotary drilling rig can be cleaned more thoroughly.