Abstract: Static loading plate tests, SPT, CPT and water preloading test of the oil tank foundation improved by stone columns’ were made in-situ. Studies of the results obtained shown as follows: ① Stone columns strengthen the resistance to seismic liquefaction of the saturated clayey silt foundation; ② Bearing capacity of the foundation was doubled; ③ Rate of consolidation of the foundation was accelerated, and the differential settlement of the oil tank decreased; ④ Initial excess pore water pressure in the foundation Was reduced.