The invention provides a method and a device for avoiding forgetting children in a vehicle. The method is characterized in that: a detector is utilized for detecting the vehicle-starting signals and the trip-finishing signals; and combined with the judgment of a driver, the information on the existence of a child will be transmitted to a central processing unit (CPU) for treatment. If there is a child in the vehicle, the CPU will send an instruction for movement to the preventing device, thereby adopting actions to avoid forgetting the child in the vehicle. The device of the utility model comprises a power supply, a vehicle starting test apparatus, an inquiry unit, a trip-over test device, a preventing device, and a central processing unit (CPU). The device helps avoid forgetting children in the vehicle.