Abstract: A secure beamforming （BF）algorithm with imperfect channel state information （CSI）is proposed for a satellite and sky cooperative network with the help of UAV relay. Firstly, a multi-objective optimization problem（MOOP）is formulated to maximize the achievable secrecy rate and to minimize the transmit power. Then, considering that it is difficult to obtain the perfect CSI of eavesdroppers and out-network users, a method combing weighted sum method, the solution method of angular discretization and successive convex approximation are proposed to convert the non-convex multi-objective problems into a convex one, and the semidefinite programming is adopted to solve the problem. The simulations confirm that a better compromise can be achieved between security and power consumption by the proposed algorithm.