The invention provides a braking warning system based on infrared rays, relating to the technical field of traffic safety. The braking warning system comprises a first infrared emission unit (1), a second infrared emission unit (2), a camera (3), a central processor (4) and a buzzer (5). The first infrared emission unit (1) and the second infrared emission unit (2) are installed at the rear of a car at a fixed interval. The camera (3) is installed at the front part of the car. The central processor (4) receives and processes infrared signals captured by the camera (3). The invention further provides a braking warning method based on infrared rays. The braking warning system and warning method based on infrared rays have following beneficial effects: by installing two infrared emission units at the rear of the car at the fixed interval, infrared signals are sent behind the car at regular time intervals; after the camera behind the car captures the infrared signals, relative acceleration of the car is measured after the central processor processes the infrared signals so that a judgment is made as to whether the car is expected to collide with another car; and therefore a driver is reminded to brake within the safe distance.