The invention discloses a road safety height limit assembly. The road safety height-limit assembly comprises an inverted U-shaped frame (1) which is mounted on bridge crossings and road crossings for setting the corresponding height to limit the height; a base (2) is arranged on the bottom of two ends of the frame to stably fix the frame on the ground, an expansion link (3) is installed on the vertical direction of the frame for self-defining adjustment of height; a detection module (4) is positioned on the transverse direction of the frame, and can control a prompt module according to the detected vehicle height; the prompt module (6) is installed on the frame, and can send prompt message if the vehicle is higher than the height limit; the way for prompting message is sound or LED light; the height limit of the vehicle is self-defining, and vehicles can be prevented from collision accidents according to the automatic detection of the height prompt of different vehicles.