Abstarct: This thesis aims to develop a suitable method for accurate modeling and dynamic analysis of this nonlinear compliant robot with large deformation. It is essential to pay attention to the computation time and accuracy in the modeling toward the control implementation. The issue arises here because computation complexity at the cost of interpretability increases as model accuracy increases. The goal is to offer an appropriate strategy for solving nonlinear motion equations of a precise model at a low computational cost. The internal channel networks embedded within a soft structure can be a fruitful mechanism for creating and activate actuators in the research fields of soft robotics. The deformation of the supporting elastic structure from the pressurized viscous fluid into the channels needs an accurate investigation. In this modeling, the compliant actuator is considered the Euler-Bernoulli beam with large deflection and nonlinear strain. After implementing Hamilton’s principle, the assumed mode method is used to achieve the mathematical model in terms of the multi-mode system that is more similar to the flexible nature of the actuation system. Steady-state dynamics is investigated by combining the complex averaging method with arc-length continuation. The accuracy of the proposed modeling is validated by comparing simulation results to those obtained with a nonlinear finite element method, numerical method, and Ansys software. It shows that only one-third of the DOFs used for the FEM are sufficient to obtain equivalent converged solutions with the proposed model. The effect of nonlinear strain and multi-mode consideration in the analysis of the proposed modeling is investigated. It is advantageous to analyze the system performance by looking into the geometrical parameters and fluid properties. Comparing the results of the present dissertation with other results shows that the proposed method can be used with good accuracy and low computational cost for dynamic modeling of compliant robots with large deformations. Then we study the modeling and analysis of a compliant tail-propelled fish-like robot by the proposed method and use a fluidic actuator as a fish tail. Because of the advantage of low computation cost despite nonlinear model characteristics, this approach can provide essential guidelines for the motion control of the compliant robotic fish.