1. A method for updating a background model based on depth, the method comprising: receiving, in response to the occurrence of a predetermined background updating condition, one or more depth images captured after a time when the predetermined background updating condition occurs; obtaining, based on an original background model, foreground images in the one or more captured depth images, which are newly added compared with a depth image at the time when the predetermined background updating condition occurs; for each of foreground pixels in each of the newly added foreground images, comparing a current depth value with a previous depth value before the time when the predetermined background updating condition occurs; and updating, when the current depth value is greater than the previous depth value, the original background model as the updated background model by using the foreground pixel in the newly added foreground image.