To study penetration performance on aramid composite by fragment simulating projectile, ballistic impact experiments were performed on 15 mm aramid composite penetrated by 4.5 g fragment simulating projectile. The results show that linear relationship exists between initial velocity and residual penetrating velocity, and a maximum value of energy absorption per areal density occurs. Then, engineering analysis was given on the aramid armor penetrated by fragment simulating projectile. The calculating formulas of ballistic velocity and residual velocity for aramid composite were given. The result of anylytical method agreed well with the test results. Then maximum value of energy absorption per areal density was put forward, finally, the characterization method of aramid composites penetrated by fragment was discussed.