An elongated "rigid-flexible coupling" pneumatic flexible driver with compressed gas as the power source is designed. The driver adopts an inner and outer nested structure, with an elastic airbag inside and a restraining spring outside, which can effectively improve the rigidity of the driver. In order to study the influence of restraint springs of different stiffness on the statics performance of pneumatic flexible actuators, experimental methods were used to study the relationship between actuator axial elongation deformation, driving force and working air pressure with different spring wire diameters. The experimental results show that the extension of the actuator increases non-linearly with the increase of the working air pressure. Under the same working air pressure, the diameter of the constrained spring wire is negatively correlated with the extension of the actuator; when the elongation is zero, the actuator has an axial direction The driving capacity is the largest, and the maximum driving force of the actuators with different stiffness is the same, which is positively related to the working air pressure. This research provides a feasible solution for the further application of the elongated pneumatic flexible actuator in the soft robot.