Abstract: ‍ ‍Due to the different subarray division methods and the influence of ocean environment noise， it is difficult for multi-beam echo sounder （MBES） to obtain high quality phase difference curve in edge beam， resulting in large error in zero crossing detection. To address the above problem， this paper proposes a multi-subarray phase detection method based on the quality factor. Firstly， through theoretical derivation and analysis， it is determined that subarray element overlap leads to biased phase difference estimation at low signal-to-noise ratios. To avoid this bias， this paper adopts a multi-subarray structure with non-overlapping elements between subarrays for subarray partitioning. Secondly， the subarray spacing is optimized based on the maximization of the minimum criterion， and multiple subarrays are used to deconvolve the phase difference curve. Furthermore， the expression of the quality factor for second-order polynomial fitting of the phase difference curve is derived， and the phase difference data is selected based on the quality factor as the evaluation criterion. Finally， a recursive least squares algorithm is designed for phase difference sequence extraction to improve computational efficiency. The simulation results show that the method proposed in this paper can realize the unbiased estimation of the phase difference curve， improve the understanding fuzzy robustness by using multiple subarrays， and obtain smaller sounding errors in the edge beam than that in the position deviation indication method and the split beam method. Experimental data further validates the engineering practicability of the proposed method.