This paper evaluates four designs of circumferential pneumatic soft-actuator and shows its application to a soft stomach robot. The testing of the design is based on a finite element analysis of geometrical displacement and related pressurisation. In a biological human stomach, the antral contraction wave deformation is represented in a ring-shaped structure. The inspiration of such behavior of deformation leads to a proposal of a ring-shaped soft actuator. The proposed actuator includes a pneumatic system with multi-chambers and multi-layers to produce a deformation similar to that in the stomach organ. There are four proposed chamber designs: semicircular, cylindrical, ellipsoidal and semirectangular. The body of the actuator is made of soft material (silicone) with a high stress/strain relationship in order to exhibit large deformation behavior. In this article, the evaluation of four possible shapes of pneumatic chambers of the circumferential soft-actuator is examined and compared by Finite Element Analysis to simulate the displacement of each soft actuator. Two different methods are used in the experiments: (1) we applied the same pressure to all actuators and compare the displacements, (2) we applied different pressures to obtain the maximum pressure in each actuator before distortion and then examine the maximum displacement that can be achieved.