Abstarct: Generally safety of every structure built on soil, depending on strength and hydraulic state of in view subsoil. Namely with increase of underwater level in soil, excess pore water pressure due to structure loading increased and soil strength decreased that result in instability. Settlement due to loading is considered as factor for stability monitoring that formed from two stage, part of settlement happened during loading (transient settlement) and part that happened after loading in long term (consolidation settlement) and the time of that may be last several day till several year baxsed on available condition, for example if subsoil include of saturated clayey soil, soil settlement not completed in this stage and may be continued long after structure operation. Conventional methods employed for underwater drainage and after that increase of consolidation settlement rate, include of stone columns (gravel columns) and embankment construction. In recent years, using prefabricated vertical drains with embankment construction as preloading, drainage speed and consolidation settlement rate increased. Over time by applying vacuum in prefabricated vertical drains more speeds has been given to consolidation process. In this study, in order to investigate the effect of bed soil type on improvement methods selection (embankment, embankment with prefabricated vertical drain, prefabricated vertical drain with vacuum, embankment with prefabricated vertical drain and vacuum), numerical modeling with Plaxis software used. In order to investigate the effect of soil type, four ground types is considered that in each type one optimum improvement methods has been introduced. Results showed that soil type has considerable effect on soil improvement method determination, so that in ground type one, embankment preloading method, in ground type two, embankment preloading with prefabricated vertical drain method, in ground type three, vacuum pressure preloading with prefabricated vertical drain method, and in ground type four, coupled embankment and vacuum pressure preloading with prefabricated vertical drain, been the most effective improvement method, that the amount of time reduction in improvement process of ground types 2,3,4 than state that embankment used, been 89.4, 99.71,99.2 percent respectively.