Disclosed is a method for warning of a traffic light based on machine vision technology and a detecting device thereof, the method includes the following steps: mounting a detecting device for detecting a traffic light on a top part of a vehicle, and mounting a notification assembly of the detecting device inside the vehicle; receiving a detection request of traffic light status, increasing a height of a camera of the detecting device, and obtaining current image information of the traffic light; determining the traffic light status in the current image information of the traffic light using the machine vision technology, sending a determined result to the notification assembly, and providing a driver with current traffic light information using the notification assembly.