Multi-monomer grafted polypropylens (PP-g-(GMA-co-St)) was used as a precursor of／in-situ compatibilizer for incompatible blend of poly(butylene terephthalate) (PBT) and polypropylene(PP). The formation of PBT-g-PP copolymer with addition of PP-g-(GMA-co-St) was confirmed by means of MFR and FT-IR measurements because the epoxy group in glycidyl methacrylate (GMA) of PP-g-(GMA-co-St) reacted with the terminal carboxylic acid group in PBT．Thus the PBT-g-PP copolymer acted as a compatibilizer between PBT and PP during the melt blending．The changes in morphologies of PBT/PP／PP-g-(GMA—co-St) blends with different contents of PP-g-(GMA-co-St) were investigated using scanning electron microscopy (SEM)．The addition of PP-g-(GMA-co-St) markedly improved the morphologies of the blends

and uniform and fine dispersed phase was observed with size being about 0.2 μm for PBT／PP-g-(GMA-co-St) (70／30) blend．Micro-phase separated structure formed in the blend was found by means of transmission electron microscopy (TEM)．The addition of PP-g-(GMA-co-St) also greatly improved the mechanical properties of PBT/PP blends

particularly for PBT／PP／PP-g-(GMA-co-st) (70／20／10)blend．It should be noted that the tensile strength of the blend was kept with the increasing of the lzod impact strength and elongation at break．