Considering the common fragment is bad at igniting diesel oil box, in order to develop a new efficient ammunition, in this paper, a math model was set up to calculate the concentration of diesel steam, the ability of fragments igniting diesel oil box was analyzed, and an experiment was did to check it. The results indicate that with the velocity becomes faster, the concentration of diesel becomes lower; When the fragments impacts on the liquid part of the oil box, the concentration of diesel steam is higher than the flammability limits, the oil boxes are not ignited; HYDRAULIC RAM happens in the oil box, and the shell of oil box is destroyed.