Abstract: Though a completed procedure implemented in MBS data processing, an ideal sounding result still can not be achieved, the multibeam echo sounding data still comprehensively influenced by the residual errors, such as the measurement errors of sound speed profile (SVP), representative error of SVP , alignment deviation error of MBS transducer, and attitude error. The synthetic influence of these residual errors on sounding result takes on systematicness, is difficult to be separated and weakened by traditional methods, and is especially obvious in the area of ??deep water and fringe beam of MBS. Therefore, a new method based on the blend of the long wave and the short wave of seabed topography is put forward in this paper to weaken the influence of these residual errors, and its efficiency has been proved by experiment.