Weapon lightweighting is a research emphasis of ordnance industry, which can improve the combatant ability of the individual soldier. In this study, the application of engineering plastics and their composites in small arms has been profiled; the advantages and requirements of engineering plastics using in the field of small arms has been summarized; the development direction and trend of small arms in the future has been analyzed. The weight of small arms can be reduced and the performance can be greatly improved by utilizing of engineering plastics and their composites to prepare some parts, which is able to accelerate the process of weapon equipment lightweighting.