Abstract: The principle of transmitting Digital Beamforming(DBF) of Uniform Linear Arrays(ULA) is introduced.The given null control method for transmitting DBF is studied.Of the proposed method,the given null control is treated as a constrained optimum problem,and the optimal weight vector of transmitting DBF is derived by Lagrange multiplier approach.Finally,the computer simulations are done.The simulation result shows that the proposed method is practicable and effective.