Original and/or functionalized nanosilica particles (NSIx, FNSIxmy) with a quoted specific surface area of 100, 300 and 600 m2/g, respectively, were used to investigate the influence of specific surface areas of nanosilica particles on ultradrawing and ultimate tensile properties of UHMWPE (F100), UHMWPE/nanosilica (F100NSIxz) and UHMWPE/functionalized nanosilica (F100FNSIxmy-z) fibers. The specific surface areas of well dispersed FNSIxmy nanofillers in F100FNSIxmy-z fibers can positively affect their ultradrawing，orientation, ultimate tensile properties and “micro-fibrils” morphologies. Excellent orientation and ultimate tensile properties of UHMWPE/nanofiller fibers can be prepared by ultradrawing the Fi00FNSIxmy-z as-prepared fibers with optimal contents of the best prepared FNSIxmy particles well dispersing in the as-prepared fibers. The ultimate tensile strength (af) value of the best prepared F100FNSI600 m9-0.0375 drawn fiber reaches 7.6 GPa, which is about 1.7 and 2.3 times of those of the F100FNSI100m3-0.075 and the best prepared F100 drawn fibers without addition of any nanofiller. Specific surface area, morphological and Fourier transform infrared analyses of NSIx, FNSIxmy particles and/or investigations of thermal, orientation factor and ultimate tensile properties of as-prepared and/or drawn Fi00FNSIxmy-z fibers were performed to understand the above improved ultradrawing and ultimate tensile properties of the Fi00FNSIxmy-z as-prepared and/or drawn fibers.