The area coverage rate is dramatically improved by using the multireceiver technique. However, this configuration leads to the complexity of the synthetic aperture image formation. In order to solve this issue, the target based on the phase centre approximation (PCA) is to be reconstructed. The data related to the multireceiver SAS system is coerced into the data like traditional monostatic synthetic aperture sonar (SAS) system. Then, the data can be processed by traditional imaging methods. In this paper, the chirp scaling algorithm is exploited as an example. Moreover, the influence of some important steps with the monostatic conversion, i.e. pulse compression in the range dimension and the micro range cell migration correction (RCMC), is further discussed in detail. The simulations show that the presented method can focus the target well.