Abstract: As a good choice of more powerful automatic batymetric survey techniques with high accuracy and full coverage,the multibeam strip sounder equipped for the first middle pelagic survey vessel made in China has been brought out recently.Based on systematic analysis to the error sources and error properties of multibeam soundings,the theory models for error processing will be presented in this paper.Especially based on trend surface analysis,the methods for gross error process and strips mosaic,and heading correction will be stressed.