In this paper, the carbon nano-fibers (CNFs) were used to improve the performance of sulfonated poly(styrene-b-[ethylene/butylene]-b-styrene) (SSEBS) composite actuator. The SSEBS actuator, which was developed in our previous study, does not have good electromechanical performance because the SSEBS ionic polymer is too flexible and soft. CNFs as a reinforcement for the polymer membranes greatly increased the bending performance of the SSEBS actuators. The surface and cross-sectional morphologies of the CNF-SSEBS actuators were investigated by SEM observation. The results show that carbon nanofibers were homogeneously dispersed in the SSEBS polymer matrix without local agglomeration. The bending responses of the CNF-SSEBS composite actuators under step inputs and sinusoidal excitations were compared with those of the pure SSEBS actuator. The tip displacement of the CNF-SSEBS actuator was much faster and larger than that of the pure SSEBS actuator. (C) 2008 Elsevier Ltd. All rights reserved.