Abstract: Polypropylene wax, grafted by methacrylic acid, was used for a glass fiber/polypropylene composite. A modified single fiber fragmentation technique was introduced to conveniently measure interfacial shear strength of the glass fiber and polypropylene. Data indicated that the values of interfacial shear strength of specimen which glass fiber coated with a silane coupling agent and grafted or ungrafted polypropylene wax would be elevated remarkably than that of the composite which glass fiber treated with the silane only. It was concluded that the modified polypropylene wax could play a significant role in the glass fiber/polypropylene composite and the silanes only had a little influence on the specimen.