The invention discloses a measurement method for facilitating measurement of the internal diameter of a deep hole. A measurement device is arranged on the deep hole; an infrared sensor on the measurement device is used for sensing the position of the deep hole; a conveyor belt under the measurement device is used for carrying out conveying; when the infrared sensor senses the position of the deep hole, a telescoping rod connected to the conveyor belt downwards stretches to reach the interior of the deep hole; four eddy current displacement sensors connected to the side face of the telescoping rod begin to measure the distance between themselves to the inner wall of the deep hole; every two of the eddy current displacement sensors are opposite to each other and two straight lines of two groups of the eddy current displacement sensors are mutually perpendicular; the eddy current displacement sensors send measured data to a calculation module; and the calculation module adds the data of two opposite eddy current displacement sensors with the diameter of the telescoping rod, averages the obtained data, sends the obtained data to a controller and sends the obtained data to a display for displaying.