In order to obtain low probability of intercept, it is required to form nulling in the transmit pattern for the phased radar. To solve the problem, a fast phase-only pattern nulling algorithm is proposed in this paper. First, dummy interferences are introduced according to the nulling angles, and the interference covariance matrix is calculated; then the mathematical model for forming nulling is established by minimizing the array output power; last, the phase-only weight can be obtained by the single coordinate algorithm. The experimental results demonstrate the correctness and effectiveness of the proposed approach.