In this Paper, modeling, open-loop analysis and design of the centralized control system with the nonlinear control law of the dual-body UAV are discussed. In the two-body configuration, two completely identical aircrafts are connected to each other using a one-degree-of-freedom connection around the longitudinal body axis(hinge at the tips of the wings). The 6DOF dynamics of the of the two-body UAV is modeled using the Newton-Euler method. Changes in the behavior of two-bodied aircrafts in the form of different modes have also been investigated. Although the equations governing the flight of a double-body UAV are fully nonlinear and coupled, the nonlinear control laws for multi-body UAV have not been found in the articles in this field. Also, the control system developed by different teams is only decentralized, which increases the cost of the control system. In the present paper, the centralized control system with the nonlinear control law is proposed to solve the mentioned problems. The numerical simulation results show that the nonlinear control system has a better performance than the linear control and the time response graphs are very smooth and without any overshoots. The deviation angles of the control surfaces and trust levels are also limited and reasonable.