A digital test system was presented, used to measure the angle of shot gun bore axis deviates from exit surface. Based on the principle of laser tracker space coordinates measurement, by measuring the 3D coordinates of the gun barrel, the system accounts for the linear equation of space before and after the adjustment of gun, thus the deviation angle of the gun was calculated, and the problems of low precision, low efficiency, too much staff and structure dispersion were analyzed in the measurement method of gun bore axis deviation angle from the exit surface in view of the current GJB method. Comparing the experimental measurements with the current GJB method, the experimental data show that by using this method to measure the deviation angle of the gun, the efficiency and accuracy are improved obviously.