A passive location method to long baseline antenna array is proposed. In this method, an array antenna is embedded into a long baseline system with tri-antenna firstly. According to the principle that the angle between the target and the long baseline is implied in the phase difference information, the angle changing rate can be estimated from the phase difference of the angle between the target and the long baseline. The actual direction of the target can be measured by the array antenna. The position parameters of the target are obtained thereafter. The method can be applied to locate the target by using only a single pulse. The simulation results verify the validity of the proposed method.