Underwater gliders are a new class of autonomous underwater vehicles, which are energy efficient, inexpensive and can be utilised for long duration mission. They use a ballast system and moving mass to glide in the saw-tooth path pattern through the ocean water column. This paper presents the dynamic model of USM underwater glider based on slender-body theory. In this work, a moving mass implementation and hydrodynamic interaction among hull, wings, and tail are included. The simulation results illustrate the dynamic characteristics and its response over velocity and angle of attack. In the results, the equilibrium angle of attack and velocity of underwater glider at minimum drag force can be obtained based on specific dimension. In this work, USM underwater glider produced minimum drag force at 1.7° angle of attack with velocity of 2.7 m/s. In addition, the effectiveness of a moving mass actuator also presented in the simulation results. This model will be used for further works in developing an optimized USM underwater glider with six degrees of freedom, including designing an establish full mathematical model of its motions and control algorithm.