The received signal of traditional four elements ultra-short baseline positioning system is affected by noise seriously. The location result may have phase ambiguity and low reliability. To address this issue, a virtual element location method is proposed, which is based on flat array beamforming. Firstly, the method divides the uniform square array into four sub-arrays symmetrically. By sub-array beamforming, virtual elements are projected to form a four-element cross array respectively. Then, the direction of arrival estimation method of four-element cross array is implemented to calculate the target direction. The achieved result that has a large deviation from the previous results is discarded. Otherwise, it is used as the reference direction of the next ping data to form a feedback loop and improve the positioning accuracy. The complexity of the algorithm is significantly lower than that of traditional eigen decomposition positioning algorithm. The simulation shows the positioning performance is obviously better than the traditional four-element positioning algorithm. Using the sea trial data to analyze the feasibility of the algorithm, it can be seen from the result that the algorithm can effectively improve the accuracy by increasing the SNR of the received signal.