An early warning method and a device for preventing a wheelchair from tipping over are described. The early warning method includes projecting a laser light pattern, scanning the laser light pattern, making a comparison to determine whether the ground is a barrier terrain, and issuing an early warning to the user in situations of risk. The laser light pattern is projected onto the ground and compared with a standard pattern. The early warning is generated and is one selected from a group consisting of a beep, a warning message and a vibration to alert the wheelchair user to the danger of the barrier terrain.