According to the force conditions of a submersible robot swimming in a fully-filled pipe, a dynamic model describing the 6-DOF （ Degree of Freedom） spatial motion of the robot is established based on Euler parameters （quaternion）. Then, for a robot swimming along the planned trajectory in a specific three-dimension pipeline, the fluid resistance is calculated with the CFD simulation software Fluent and is substituted into the proposed model to obtain the forces of the robot in the Mathematica environment. Moreover, a dynamic simulation utilizing the proposed model is performed to obtain the needed driving force when the robot swims in a determined crooked pipeline. With the use of Euler parameters （ quaternion）, singularities are effectively avoided.