Abstract: The glass fiber (GF) was corroded in the diluted acid solution for different times, and subsequently the GF/isotactic polypropylene (iPP) composites were prepared. The effects of the acid corroded GF on the interfacial morphology of GF/iPP composites were studied via the polarized optical microscope. The result show that the GF corroded for 4 h exhibits the nucleation ability to form novel banded nuclei in the early stage of the crystallization, and the β-transcrystallinity can be developed from these nuclei finally. In addition, the isothermal crystallization at 142 ℃ of this composite shows that GF corroded by acid for 4 h has nucleating duality towards matrix, viz., it has both β nucleation ability and α nucleation ability.