A traffic light image processing method and device, a computer system, a roadside device, and a storage medium are provided. The method includes: acquiring image data of a traffic light from a roadside sensor, the image data of the traffic light including a sequence of image frames over time, and the traffic light including at least two light heads; performing difference processing on two temporally adjacent image frames to obtain a difference image, a pixel value of each pixel point of the difference image being equal to a difference value of corresponding pixel points of the two temporally adjacent image frames; performing thresholding processing on the difference image to obtain a thresholding processed difference image; and determining a switched-on light head in the traffic light based on the thresholding processed difference image.