AbstractBased on the preferred plane theory，the sensitive preferred stratum is classified into 3 grades，from whichthe stratum of fine silt一1 and silt—fine—sand一7 in the foundation of Suzhou-Nantong(Sutong)bridge areverified to be the sensitive preferred stratums．To Suzhou- Nantong bridge，the super long piles will be used，and the body of the piles will be all in the soils．So the engineering geology problems of the sensitive preferredstratum include：bearing capacity of the piles，rheology of the soft soil and sand liquefication．The study resultsindicate that because of the sensitive preferred stratum ，the bearing capacity of piles will be reduced，therheology of the soft soil will affect the stability of the pits，by the experiments the parameters of the rheologymodel are gotten．Under the effect of the quaky loads，the sands is easy to be liqueficated，then the stratumswill lose bearing capacity．