The ionic polymer metal composite (IPMC) is a novel smart polymer material, many potential application for low-mass high-displacement actuators in biomedical and robotic systems have been shown. Although several nonlinear models have been proposed in precision displacement control, none has finally been adopted absolutely for identification of some physical parameters is still difficult. In this paper, for a IPMC, some physical parameters are small enough for influence of displacement deformation, which are considered as uncertainties of model. To avoid the influence of the unknown uncertainties, an improved operator-based nonlinear model with uncertainties is proposed. To confirm the effectiveness of the proposed model, an operator-based nonlinear control for the IPMC setup is designed. The effectiveness of the proposed model is confirmed by simulation results of the operator-based nonlinear robust control system and experimental results of a IPMC setup.