The utility model discloses a system for starting a flasher after collision. When a vehicle is collided at a set degree, an alarming system is opened at the first time to make an audible and visual alarm, so that running vehicles are alarmed to give way so as to avoid secondary injury accidents; and the system comprises a vehicle body controller, a vehicle speed sensor, a collision sensor and the flasher, wherein the vehicle body controller is connected with the vehicle speed sensor, the collision sensor and the flasher.