To the problem of how to design a multi-UAV formation keeping optimization model,we combined the kinematic equation of multi-UAV,performance index and constrained condition together to construct a constrained optimization problem.After transformation was made to the performance function to decouple the optimization problem,we introduced the Lagrange multiplier vector to construct a Lagrange function.To the two classes of optimization variables,the basic and dual variables,we found that all the basic and dual variables could be formulated to the expressions of one dual variable.Then the gradient projection method from the convex optimization was proposed to solve this dual variable.And the other optimization variables could also be obtained through simple substitution.Finally,the effectiveness of the proposed strategy was confirmed by the simulation example results.