The water-soluble terpolymers were synthesized in two steps, containing esterification of polyethylene glycol (PEG) and 4-amino benzoic acid without protection of its amino group, then copolymerization of aniline from both end of amine-terminated PEG via an interfacial polymerization method. The chemical structure of triblock copolymers was determined by FTIR and (HNMR)-H-1. The thermal behavior, morphology and electroactivity of terpolymers were also investigated by thermogravimetric analysis, field emission microscope (FESEM) and cyclic voltammetry (CV), respectively. Uniform nanofibers consisting of blends of (PANI)(n)-b-PEG-b-(PANI)(n) terpolymers and polycaprolactone (PCL) were prepared using electrospinning technique. The FESEM was also used to investigate the electrospun nanofibers produced from different molecular weight of PANI/PEG/PANI terpolymers and PCL (30/70). The CV measurements of blends confirmed the preparation of electroactive nanofibers. The presence of terpolymers enhanced the spinnability of solution and significantly reduced the bead formation. This novel system opens up new and interesting opportunities for applications such as electroactive scaffold for tissue engineering.