Abstract: The particle swarm optimization algorithm（PSO） is introduced into the ballast adjustment calculation for refloating a grounded ship, which allows the design of the adjustment plan to get rid of trial-and-error experiments. A theoretic model of grounding force on ship is built. The GHS software is used as the stability resolver. The optimal ballast in every hold（cargo tank） is decided by PSO algorithm for minimum grounding force on the ship. The volumes of ballast in holds（cargo tanks）, as the optimized factors, are fed to GHS software for stability checking via a Python program. Through iteration of the series of calculation, the ballast scheme for minimum grounding force is generated. This method was used for refloating the oil tanker “Dixiang” successfully.