Provided in the present invention is a method for calibration in 3D modeling: (1) capturing an image of object A; (2) moving and/or rotating a capturing device until object B enters a capturing range, capturing multiple background images while moving and/or rotating the capturing device; and (3) capturing an image of object B, where object A and object B are not in the field of view of the capturing device at the same time; object A is a calibration object, object B is a target object; or, object A is a target object, and object B is a calibration object; multiple calibration points are provided on the calibration object; and the coordinates of the target object are calibrated on the basis of the coordinates of the multiple calibration points. The calibration of the absolute size of a long-distanced target object is implemented by means of the method of continuously photographing while moving or rotating.