Abstract: Since the mass of the soft manipulator is distributed along the length of arm continuously, when Lagrange method is used to establish the dynamic modeling of the soft manipulator, it involves complex integral calculation. The discrete centralized mass model reduces the complexity, but the accuracy is limited. In this paper, in order to improve the accuracy and efficiency of dynamics modeling and simulation, of the soft manipulator, the modal method is adopted to describe the kinematics of the soft manipulator. Then, considering the dynamic characteristics of the soft manipulator from the energy point of view, it is found that the calculation of rotational kinetic energy generated by the angular velocity is complex, which affect the efficiency of solving the dynamics equation. However, the percentage of rotational kinetic energy in the process of dynamic modeling is less than 3% of the total kinetic energy on a given condition. Consequently, the effect on the dynamics results is small and it can be ignored in the modeling process. Further, a dynamics model of the soft manipulator is proposed based on the concentrated mass description of the center of mass. The continuous distribution mass of the soft manipulator is equivalent to the concentrated mass located in the center of mass. The kinetic energy equivalent coefficient is calculated based on the statistical method. Then, the kinetic energy matching between the two is realized by the kinetic energy equivalent coefficient and the calculation accuracy is improved. The simulation results show that compared with the centralized mass model which usually places the concentrated mass at any position (for example, the midpoint or end of the soft manipulator), the model takes into account the accuracy of the continuous distributed mass model and the calculation efficiency when using the centralized mass model. The model proposed in this work can obtain the dynamics characteristics of the soft manipulator accurately and efficiently, and the numerical calculation is stable.