A monitor system includes at least one three-dimensional camera circuit and a controller. Each of the at least one three-dimensional camera circuit is used for capturing a plurality of images including an object, and generating a depth map corresponding to the object according to the plurality of images. The controller is used for determining a plurality of feature points corresponding to the object according to the plurality of images or depth map, determining relative coordinates of the plurality of feature points according to the depth map, generating external information corresponding to the object according to the relative coordinates of the plurality of feature points, and generating monitor information corresponding to the object according to the external information corresponding to the object and reference parameters corresponding to the object.