The invention discloses a mobile-terminal-based intelligent pre-warning system capable of preventing a pedestrian from being hit by a car. The intelligent pre-warning system comprises a mobile phone, a rectangular transparent shell, a ball, a distance sensor, a gravity center block, an MCU, a loudspeaker and a vibration motor, wherein the transparent shell is mounted at the top of the mobile phone and provided with a spherical hollow space inside, and an annular track is machined along the inner wall of the spherical space; the circular heads at two ends of a needle-shaped rotary shaft are embedded into the annular track, and the rotary shaft rotates along the annular track; the ball is provided with a rotary shaft mounting hole along the horizontal direction, the distance sensor is mounted in front of the ball, and the gravity center block is arranged at the bottom of the ball; the rotary shaft penetrates the rotary shaft mounting hole in the ball, and the ball can rotate around the rotary shaft; the MCU and the vibration motor are mounted in the motherboard of the mobile phone, and the loudspeaker is mounted on the shell of the mobile phone. When a smartphone addict walks on a road and a car in front drives towards the smartphone addict, the loudspeaker gives out a prompt tone of 'watch out the car', and the vibration motor vibrates to remind the pedestrian to pay attention to safety.