Ultrahigh molecular weight polyethylene (UHMWPE)/WS2 nanoparticle fibers were prepared by adding WS2 nanoparticles treated by coupling agent in the precursor solution of UHMWPE. The influence of WS2 nanoparticles on the microstructure and properties of UHMWPE fibers was characterized by SEM, TGA, mechanical property measurement and bullet-shock test. The results showed that WS2 nanoparticles can be uniformly dispersed in the UHMWPE fiber. After incorporating of WS2 nanoparticles, UHMWPE fibers became stiffer and tougher than the pristine ones. Particularly, the modulus of the fiber increased from 1203 to 1326cN/dtex. Furthermore, UHMWPE/WSfibers showed an improved thermal stability.