Abstract At present, there is little research on the strength simulation calculation method of local steel structure at the joint between the fin stabilizer and hull of SWATH at home and abroad. Aiming at the problems of high-stress levels and difficult local strength of the local structure at the joint of SWATH submersible and stable fin, this paper, based on APDL language, takes a SWATH ship as an example, establishes a whole ship simulation model, analyses and studies the modeling scope, modeling requirements, boundary conditions, and loading methods of the local calculation model of stable fin, and puts forward an efficient simulation calculation and analysis method, namely sub-model method, which is suitable for the local strength calculation of stable fin, and provides guidance for the structural design method of the stable fin of SWATH catamaran.