It has small field of view and weak light in the detection environment of gun barrel structured light detection system,which makes traditional calibration methods have larger limitation.A calibration method is proposed based on the structured light according to this problem.A calibration cylinder includes various structure information is designed according to 155 caliber gun,The relationship between the depth of groove in the calibration cylinder and the distance between the structured light stripes is obtained by processing the image of the inner surface of the calibrated cylinder with this method,and the parameter of the detection system is calibrated.The wear quantity of the inner diameter of the barrel is detected by the system.The experimental results show that the absolute error is not more than 0.01,which can meet the requirements of gun field detection.