The invention discloses a running vehicle anti-collision system and method. The method includes the steps that a distance measurement sensor detects the distance between a current running vehicle anda running vehicle ahead; an acceleration sensor of the vehicle ahead detects the running acceleration value of a(ahead) of the running vehicle ahead, and a vehicle controller of the vehicle ahead transmits a(ahead) through a transmitter of the vehicle head; a current vehicle controller judges whether or not a transmitted former distance value is larger than a latter distance value; if yes, a current braking controller is called to judge whether or not the latter distance value is smaller than a set maximum critical value and larger than a first set intermediate critical value; if yes, a current braking execution mechanism is controlled to brake to make a(current) detected by a current acceleration sensor smaller than a(ahead), and whether or not the latter distance value is smaller than the first set intermediate critical value and larger than a second set intermediate critical value is judged; if yes, braking control is conducted to make a(current) equal to a(ahead), and whether or not the latter distance value is smaller than the second set intermediate critical value and larger than a set safety distance value is judged; if yes, braking control is conducted to make a(current) larger than a(ahead).