In order to solve the problem that the data of the inner wall detection system of the body tube is large and the data processing is complicated, the parameter of the body tube is difficult to obtain, and the data processing method of the inner wall detection system of the gun barrel is proposed. On the basis of completing the construction of the gun barrel detection system, aiming at the special structure of the body tube and the characteristics of the data collected by the laser displacement sensor, the method of reducing the inner wall contour of the body tube and the method of separating the line data are proposed. The parameters of the inner wall of the body tube are obtained based on the least squares method. And the error of the system is analyzed and corrected, which improves the accuracy of the system. The experimental results show that the radial error of the system is less than 0.01mm, the error of the abnormal data correction is less than 0.01 mm, and the data processing method is correct, which effectively solves the problem of obtaining the inner wall parameters of the gun barrel.