The measurement principles are discussed in detail for projectile dimension measurement, based on the analysis and classification of the structural dimensions of special projectiles. According to the practice in the factory, a measuring equipment is set up to measure those dimensions. Two high precision laser displacement sensors and motion controller are introduced to construct this automatic digital measurement system for digital inspection and evaluation of the key dimensions. Actual application shows that this system can effectively improve the projectile dimension measurement precision and give the error distribution. Testing result shows that the system measurement error is less than 10 microns for internal/external diameters and 100 microns for the external length. Hence the measurement system can guide the machining processes and helps to control the product quality.