Abstract: An experiment setup for the contraction force measurements of pneumatic muscles was developed for sake of the pneumatic muscle’s dynamic characteristics. The pneumatic muscle forcedisplacement hysteresis characteristics were found to be asymmetry, with nonlocal memory, weak correlation of high internal pressure,and quasi rate-independent by investigating the influence of the internal pressure,stroke,contraction velocity,contraction frequency on the pneumatic muscle’s forcedisplacement. Aiming at the problem that the existing Prandtl-Ishlinskii（ PI） model cannot predict forcedisplacement hysteresis much well,a modified PI + Dead-zone hysteresis model was developed by incorporating a modified dead-zone operator with the classical PI model. The model’s parameters were further estimated by the least square method and the model precision was compared with the classical PI model,the classical Bouc-Wen（ BW） model,PI + Polynomial model,Wang-Wen model and BW +Polynomial model. Comparative experiment results showed that the PI type models performed much better than BW model,and the modified PI + Dead-zone model can predict force-displacement hysteresis best with the absolute mean error less than 1 N and the mean variance less than 1. 5 N under each contraction condition. Furthermore,the classical PI model which possessed fewer model parameters can also estimate the force-displacement hysteresis accurately during a short contraction. Above experimental results provided a valid reference for nonlinear control of the PAM actuated servo system.