A method and an electronic apparatus for image background learning are provided. In the method, a memory space for recording multiple historical background values of each pixel in an input image is disposed in a memory device, in which the memory space is divided into a lock area and an open area. Whenever receiving the input image, a processor determines whether each pixel in the input image is a background pixel according to the historical background values recorded in the memory space. If the pixel is determined as the background pixel, the processor updates one of the historic background values recorded in the open area by using the pixel value of the pixel while keeping the historical background values in the lock area unchanged. The processor also periodically switches a location of the lock area in the memory space, so as to forget old historical background values.