Abstract: A series of poly (butylene terephthlate) (PBT)/ styrene-ethylene/butylene-styrene (SEBS) and PBT/ (styrene-ethylene/butylene-styrene)-G-(Maleic anhydride) (SEBS-G-MAH) blends were prepared by melt blending method. And the morphology, thermal and mechanical properties were studied to identify the effect of SEBS or SEBS-G-MAH weight fraction on the properties of blends. Differential scanning calorimetry (DSC) analysis indicate that all the SEBS and SEBS-G-MAH could affect crystallization of PBT, but the effect of SEBS-G-MAH on the crystallization behavior of PBT was more obvious, because of the reaction between SEBS-G-MAH and PBT hinder the movement and fold in the order of PBT molecular chains. Scanning Electronic Microscope (SEM) show that the minor phase was hardly distinguishable in the blend of PBT/SEBS-G-MAH as the result of the improvement in dispersibility, compared with PBT/SEBS blends. Dynamic mechanical properties analysis (DMA) confirms that there are well miscibility between PBT and SEBS-G-MAH and immiscibility between PBT and SEBS. All these results lead to the different mechanical and dynamic mechanical properties between PBT/SEBS and PBT/SEBS-G-MAH blends. Key works: PBT/SEBS blend, PBT/SEBS-G-MAH blend, morphology, properties