UHMWPE fiber reinforced LLDPE composites were prepared to develope the impact resistant materials. The crystallization kinetics of LLDPE with UHMWPE fiber was investigated to understand the interfacial adhesion and composite performance. The crystallization behavior of LLDPE depends on the crystallization temperature and existence of UHMWPE fiber. LLDPE matrix crystallization was affected by the inclusion of UHMWPE fiber via preceded transcrystallization on the fiber surface. The interfacial adhesion of composites was changed by cooling rate control with different crystallization behavior.