Transcrystallization of isotactic polypropylene(iPP) on different fibers (carbon fiber, glass fiber, and aramid fiber) was conducted in a temperature gradient. The Ultra-High-Module carbon fiber (UHMCF), the High-Module carbon fiber, and the aramid fiber (Twaron) showed sufficient nucleation ability to form transcrystallization of iPP in certain temperature ranges. Among them, the UHMCF showed the best nucleation ability. On the contrary, the Intermediate-Module carbon fiber, the High-Tenacity carbon fiber, and the E-glass fiber showed too low nucleation ability to form transcrystallization of iPP. One efficient way to induce transcrystallization on these fibers was proved by pulling the fibers in supercooled iPP melts. The interface shear between fiber and supercooled matrix melt on crystallization and the interface temperature gradient between fiber and supercooled matrix melt on crystallization are considered to be two very important factors for the formation of transcrystallization.