Abstract: Oligmers with different end caps (non-side, one-side and both-side capped with NA respectively) and of different molecular weights are used to toughen LP-15 resin. Discussed the toughening mechanism and the influence of end-cap and molecular weight on resins T_g and impact strength. The results showed that all systems revealed one peak in their tan δ-T curves which indicted that these tougheners had good compatibility with LP-15. In the meanwhile, all toughened LP-15 resins maintained the high T_g value of LP-15. Comparing the oligmers with NA end cap with those without NA end cap, the latter exhibited more effectiveness in improving the impact strength of LP-15 resin. To those without NA end cap, the longer the molecular chain, the higher the system toughness.