This work proposes an effective and efficient use of energy supply for a Vertical Take-Off and Landing Unmanned Aerial Vehicle (VTOL UAV). Because of low power consumption, a 2-DOF parallel mechanism is used as dual axis solar tracker, and mounted on a UAV. Then, the UAV becomes a multi rigid-body UAV which has loops of connected links. Dynamic modeling for the system is one of the most challenging engineering problems. To deal with it, kinematic constraints of all joints are determined. Undetermined close form reaction forces at joints are obtained from the kinematic constraints. Using Newton’s method, dynamic equation for each body exerted by external forces and reaction forces is formulated. A fully determined equation, which is system equation of algebraic-differential equations, is obtained by appending kinematic and dynamic equations. For both kinematic and dynamic equations, Cartesian coordinate and Euler parameter are used to describe translation and rotation motions respectively.