The ground improvement such as replacement method, vertical drain method and preloading method has been used for a longtime. However, in recent years, because of environmental problems, a soft ground improvement method, specifically DCM(deep Cement Mixing), has been increasingly used. In this thesis, the use of DCM method both in korea and in other countries has been studied. Also, a case study is introduced for the construction of a harbor structure. The case study showed that, compared with the replacement method, the DCM method resulted in significant reduction in both cost and time. No noticeable settlement was observed after the construction of the embankment. It is expected that this study will be a good example for future construction of a harbor structure in the similar case to this site.