Obtaining efficient dynamic equations of complex systems, like processes or robotic systems, are very important for control system design. While various forms of acquiring motion equations exist, state-space form has its advantages for analyzing complex systems. Among analytical and graphical techniques of finding dynamic behavior of a system, bond-graph provides straight forward way of serving linear/nonlinear equations of systems in state-space form. In this study, a four-propeller-actuated full/reduced order quadrotor spatial dynamics are investigated by using bond-graph technique. Full order dynamic behavior is obtained including motor, gear, shaft, propellers and the body. Additionally, neglecting motor dynamics, reduced order state-space representations of the system is also provided, assuming force/moment input and propeller speed as inputs to the vehicle separately. Responses of the models are compared and discussed.