Abstract: A set of all fiber optical beam breakout measurement system was designed and used in interior projectile velocity measurement. This system was based on the principle of optical beam breakout and advanced photoelectric technique. More than 100 shots were conducted on the one stage gas gun, two stage gas gun and powder gun. The result analysis showed that this projectile velocity measurement system could meet the accuracy and reliability requirements in precise physical experiments. The velocity measurement measurement extending uncertainty of this system is less than 0.8%. The velocity measurement range of this system is from tens of m/s to 7 km/s.