Polymer blends combining two or more different types of existing polymers have become a very important approach to meet specific end-use requirements without creating new molecules. However, most polymer pairs are immiscible and thermodynamically unstable, which leads to the phase separation and yields a material with poor mechanical properties. To address this challenge, block or graft copolymers pre-made or generated in-situ by reaction, whose segments are chemically identical to or have affinity with the polymer components, are often used as compatibilizers (also called interfacial modifiers or emulsifiers) to reduce the interfacial tension, promote the dispersion of one phase in another and stabilize resulting blends. This work is concerned with the compatibilizing efficiency of reactive triblock copolymer for the immiscible polymer blends. An amine-terminated triblock copolymer of Polyetheramine(PEA) and Polydimethylsiloxane(PDMS) (PEA-b-PDMS-b-PEA) were used as reactive compatibilizer for PA6/PDMS blend system. This amine in this triblock copolymer can react with PA6 to in-situ form the copolymer PA6-b-PEA-b-PDMS-b-PEA-b-PA6 as the compatiblizer. More importantly, the formation copolymer stay more easily at the interface of blend system to suppress droplet coagulation because the PEA block in this formed copolymer is immiscible with the matrix PDMS and dispersed phase PA6, which lead to a better compatibilizing efficiency comparing to the tradition reactive compatibilizer. Moreover, the compatibilizing preformance of triblock copolymer depends strongly on the chain length of PEA block.