The array formed by multiple AUVs can effectively improve target detection capabilities when each AUV is equipped with a sonar unit. However, due to the limited data processing capabilities of an AUV and its communication range limitations, efficiently forming and transforming arrays are challenging. Therefore, this article innovatively uses the optimal assignment in operations research to solve this problem and proposes an element zero method to efficiently assign multiple AUVs to arrays. First, a cost matrix consisting of the distance cost of each AUV for reaching their different assigned positions in the array is generated. Second, the preprocessing and postprocessing steps are combined to increase the number of zeros in the generated cost matrix. Third, the space tree method based on the depth-first search rule is used to find ${\bm{n}}$ independent zeros of different rows and columns. Fourth, the optimal assignment is adjusted after considering the communication range limitations. To verify the feasibility and effectiveness of the proposed method, the simulation experiments of array formation and transformation are performed for multiple numbers of AUVs. The results of this article show that the proposed method has significant advantages over the Hungarian method, and thus suggests that the proposed method is effective.