The invention relates to the technical field of radar speed measurement auxiliary installation, in particular to a radar speed measurement device with a down-turning type mounting and adjusting bracket. The radar speed measurement device comprises a traffic speed measurement device body, a longitudinal fixing rod and a horizontal mounting rod. According to the radar speed measurement device with the down-turning type mounting and adjusting bracket provided by the invention, arc-shaped adjusting openings and bottom mounting and adjusting openings are formed in the upper and lower ends of the horizontal mounting rod correspondingly, the radar speed measurement device is fixed and installed by bolt fixing of overturning mounting pipes inside the arc-shaped adjusting openings and the lateral fixing plates, meanwhile, the angle of the radar speed measurement device is changed by switching adjusting and positioning holes, the entire loading, unloading, adjustment and wiring are carried out through the bottom mounting and adjusting openings, the opening is closed by overturning sealing plates in the bottom mounting and adjusting openings, and locking and fixing are carried out by laterallocking bolts at the same time, so that the stability of the mounting manner is higher, the operation is simple, and the radar speed measurement device is more conveniently used.