Due to the limitation of material, end structure, internal friction and other factors, it is very difficult to establish an accurate mathematical model of pneumatic muscle actuator.Focusing on the internal friction of pneumatic muscle actuator and the elastic force of rubber, an improved mathematical model was established which was more practical than the ideal model.According to the structure and characteristics of DMSP pneumatic muscle actuator, the static characteristic experiment based on LabVIEW was designed and completed. Based on the ideal model curves and the improved model curves obtained by MATLAB simulation and experiment, the influence of rubber elastic force and friction force on axial contractile force of pneumatic muscle actuator was researched.It lays foundation for the further research on antagonistic joint and control strategy.