###### Abstract  
Strong nonlinearity and the relevance of time-varying dynamic parameters in the maneuverable process of water-jet propulsion were major problems encountered in the prediction of variable acceleration dynamics characteristics. The relationships between the thrust and rotation speed of a screw mixed-flow pump, drag and submerged speed of water-jet propulsion were obtained from flume experiments and numerical calculations, based on which a dynamic model of pump-jet propulsion was established in this paper. As an initial condition, the numerical solution of the submerged speed with respect to time was inputted to computational fluid dynamics (CFD) for unsteady calculation based on a user-defined function (UDF). Thus, the relationships between the acceleration, drag, net thrust, propulsion torque and efficiency with respect to time were revealed. The results indicate that the relationship between the thrust and rotational speed of a water-jet propeller is a quadratic function, which agrees well with the experimental values. The variation of submerged speed with respect to time satisfies a hyperbolic tangent function distribution. The acceleration increases sharply at the beginning and then decreases gradually to zero, especially at high rotation speeds of the water-jet pump. The variations in drag and propulsion efficiency with respect to time coincide with the step response of a second-order system with critical damping. The method and results of this study can give a better understanding of the changes in dynamic parameters such as velocity, acceleration, thrust, and drag during the acceleration of a pump-jet submersible and helped to estimate the effects of pump performance on water-jet propulsion kinetic parameters. water-jet propulsion; screw mixed-flow pump; variable acceleration; dynamics characteristics 0000-0002-4000-0002-00 response parameters were obtained by controlling the external loading frequency parameter [8; 9; 10]. [PERSON] [11] used smoothed particle hydrodynamics (SPH) to calculate the drag acting on a hull at different speeds and pitch angles, compared it with the experimental conclusions of [12]. The \"Fridsma Hull\" flow experiment was utilized to study the gliding phenomenon in maritime transport. The Nomoto model was a frequently used model that describes the basic motion of an unmanned surface vehicle (USV) [13; 14; 15; 16]. [PERSON] [17] combined the USV motion model with experimental research and gave a nonlinear mathematical model of water-jet propulsion. The results showed that the linear parameter varying (LPV) model has better operational performance for USV systems, with a hydrodynamic prediction error of less than 3%. The water-jet propulsion pump has the characteristics of substantial operating requirements and higher requirements for seasonality [18]. The hydrodynamic performance of the water-jet propulsion pump provides a reference for its design and performance prediction [19]. [PERSON]. [20] et al. studied the flow field and radial load distribution at different flow rates to verify the overall performance of CFD predictions. [PERSON] [21] and other researchers have shown that nonuniform inflow was the main reason for decline in propulsion efficiency, so nonuniform inflow conditions should be considered in the design of a water-jet pump. [PERSON] [22] compared the absorbed power and thrust with experimental data by simulating six operating conditions; good consistency was found, indicating that the geometric model was accurate and can accurately predict the performance of a water-jet propeller using CFD. The above research was limited to water-jet propulsion pumps or water-jet propulsion in direct navigation. It was mainly used in the design of propulsion pumps and was rarely used to study the hydrodynamic characteristics of water-jet propulsion under accelerated conditions.