The multi UAV formation control optimization model is decomposed into the optimization layer and coordination layer. Then the problem of how to design the multi UAV formation control trajectory can be converted to design the optimization layer and coordination layer. Firstly when the common auxiliary decision variable is known, the dual theory is used to tranform the former constrained optimization problem into a un constrained optimization problem in the optimization layer. So the optimum necessary condition is applied to obtain the control input signal.. To design the auxiliary decision variable, the gradient projection method can be applied in the coordination layer and the convergence of this method is also analysized. Finally, the efficiency of the proposed strategy can be confirmed by the simulation example results.