The traditional muzzle angle measurement method measured by optical range quadrant can’t satisfy the demand. A muzzle angle auto-measurement method based on collimation light source and PSD two-dimension sensors is provided. Adopted by the auto-measurement technology, the precision, efficiency and velocity of measurement are all improved, which solves the problems of traditional methods. The errors and precision of the new system are analyzed. According these analysis and calculation, the precision of this measurement system can gain the measurement ends.