Abstract: Preconsolidation Pressure is an indication of the stress history of a soil layer, and i& also an important parameter in settlement analysis dealing with soils having different stress histories. In this paper are reported the experimental determination of preconsolidation pressure of Shanghai soil and its variation within a depth of some thirty meters.Based upon these experimental results are also presented numerical data of the compressibility parameters, i. e., the compression, swelling and secondary consolidation indices （Cc, Ce and Ca, respectively）, as suggested by Garlanger in his studies of stress-strain relationship of soil considering stress history. Experimental investigation of"pseudo-preconsolidation pressure" due to secondary consolidation, using remoulded samples, is also reported, and based upon this a formula has been tentatively suggested for evaluating pseudo-preconsolidation pressure of Shanghai soil. It is hoped that the above-mentioned preliminary investigations may prove to be of value to studies of deformation and strength properties of Shanghai soft soil.