In this paper, a dynamic model equation of the RazakSAT® class satellite three flexible solar panels for three-dimensional dynamic studies is developed based on the coupling deformation field. In the model, each solar panel is flexible and attached to the satellite body via a fixed joint where the assumption of Euler-Bernoulli beam is applied for the solar panels. Lagrange and assumed mode method are used to develop the dynamic model of the RazakSAT® multi-body system. A comprehensive model of flexible satellite has been provided in ANSYS environment as a reference when simulating the theoretical response generated by MATLAB to show that the coupling effect on the characteristics of the flexible sub system while undergoing rigid-body rotational motion.