The invention discloses a vehicle millimeter wave radar mounting structure, system and installation method. A mounting structure for a vehicle millimeter-wave radar includes a fixing base, a radar box rotatably connected to the fixing base, and a rear locking element. A radar box includes a box body and a radar board disposed in the box body. The box body is provided with a mounting portion which is provided with a spherical protrusion. The tail portion of the fixing base is provided with a cavity with one opening end for receiving the spherical protrusion, and the rear locking element is removably connected with the fixing base. During the locking state, the spherical protrusion is in fixed connection with the fixing base. When the rear locking element is in an unlocked state, the spherical protrusion is in rotatable connection with the fixing base. The fixing base is fixedly connected with a vehicle, and the angle between the radar box and the fixing base through the spherical protrusion. When the angle is adjusted, the radar box is locked on the fixing base through retaining members, so that the designated area on the peripheral of the vehicle is detected.