The pneumatic soft actuator is the basic module of the pneumatic soft manipulator. The composite pneumatic actuator can be fabricated by selective laser sintering (SLS) 3D printing technology. However, there is a high risk of fracture in such a composite structure when its inner pressure increases to a high level. In order to make sure the safety of the pneumatic actuator, its reliability is necessary to be evaluated. In this chapter, the reliability and failure of a composite pneumatic actuator are analyzed and tested. In Sect. 4.1, the FEM model of the pneumatic actuator is developed in ABAQUS. The pneumatic experiment system is designed and developed. The shape deformations obtained from the theoretical model, FEM simulation and experiment are compared. In Sect. 4.2, the pressure bearing experiments are conducted. The pulling force of the pneumatic actuator is tested. Finally, the conclusions are presented in Sect. 4.3.