A monitoring method, wherein the method is executed by an apparatus coupled to a monitoring and photographing module, wherein the monitoring and photographing module comprises one primary camera and N secondary cameras, regions monitored by the N secondary cameras respectively cover N different regions in a region monitored by the primary camera, a focal length of any secondary camera is greater than a focal length of the primary camera, wherein N is an integer greater than 1; and the method comprises: collecting images by using the primary camera and the N secondary cameras, wherein a frame rate at which any secondary camera collects an image is less than a frame rate at which the primary camera collects an image; selecting, from the images collected by the primary camera and the N secondary cameras, M images comprising a target object; cropping the M images based on the target object to obtain M small images comprising the target object; evaluating quality of the M small images; and displaying at least a small image with a best quality evaluation result among the M small images; wherein the selecting comprises: detecting, by using a primary-camera detection thread, that M1 images in images collected by the primary camera comprise the target object, and storing the M1 images from a buffer; and detecting, by using a secondary-camera detection thread, that M2 images in images collected by the N secondary cameras comprise the target object, and storing the M2 images from the buffer; and identifying, the M1 images and the M2 images as the images comprising the target object, based on image photographing timestamps of the primary camera and the secondary cameras, target positions, and an image mapping relationship between the primary camera and each secondary camera, wherein M = M1 + M2. collecting images by using the primary camera and the N secondary cameras, wherein a frame rate at which any secondary camera collects an image is less than a frame rate at which the primary camera collects an image; selecting, from the images collected by the primary camera and the N secondary cameras, M images comprising a target object; cropping the M images based on the target object to obtain M small images comprising the target object; evaluating quality of the M small images; and displaying at least a small image with a best quality evaluation result among the M small images; wherein the selecting comprises: detecting, by using a primary-camera detection thread, that M1 images in images collected by the primary camera comprise the target object, and storing the M1 images from a buffer; and detecting, by using a secondary-camera detection thread, that M2 images in images collected by the N secondary cameras comprise the target object, and storing the M2 images from the buffer; and identifying, the M1 images and the M2 images as the images comprising the target object, based on image photographing timestamps of the primary camera and the secondary cameras, target positions, and an image mapping relationship between the primary camera and each secondary camera, wherein M = M1 + M2. detecting, by using a primary-camera detection thread, that M1 images in images collected by the primary camera comprise the target object, and storing the M1 images from a buffer; and detecting, by using a secondary-camera detection thread, that M2 images in images collected by the N secondary cameras comprise the target object, and storing the M2 images from the buffer; and identifying, the M1 images and the M2 images as the images comprising the target object, based on image photographing timestamps of the primary camera and the secondary cameras, target positions, and an image mapping relationship between the primary camera and each secondary camera, wherein M = M1 + M2.