Embodiments of the present specification provide abnormality detection methods, apparatuses, and devices for unmanned checkout. In an embodiment, a method comprising: obtaining, by a depth camera in a detection area of a photographing area for unmanned checkout, image data that comprises a depth image and a corresponding RGB image; detecting, based on the image data, one or more customers that enter the detection area for unmanned checkout using one or more of headcount detection to detect a quantity of the one or more customers or gesture detection to detect one or more gestures of the one or more customers; and in response to determining that the quantity of the one or more customers is greater than a predetermined threshold or the one or more gestures comprise an abnormal gesture, notifying a central control system to stop the unmanned checkout and trigger an alarm.